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net: reject non-address SocketAddress.parse input #64832

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net: reject non-address SocketAddress.parse input #64832

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5 changes: 5 additions & 0 deletions doc/api/net.md
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Original file line number Diff line number Diff line change
Expand Up @@ -295,6 +295,11 @@ added:
* Returns: {net.SocketAddress} Returns a `SocketAddress` if parsing was successful.
Otherwise returns `undefined`.

The `input` may contain only hexadecimal digits, `x`, `.`, `:`, `[`, and `]`.

@Renegade334 Renegade334 Jul 30, 2026

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I would personally suggest something like

The address portion of `input` must be a valid IPv4 or IPv6 hostname as recognized by the [WHATWG URL parser][]`.

^ https://url.spec.whatwg.org/#host-parsing

Anything else returns `undefined`, including other URL components such as
`user@1.2.3.4` or `1.2.3.4/foo`, whitespace, control characters,
percent-encoding, and non-ASCII characters.

## Class: `net.Server`

<!-- YAML
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10 changes: 10 additions & 0 deletions lib/internal/socketaddress.js
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Expand Up @@ -2,6 +2,7 @@

const {
ObjectSetPrototypeOf,
RegExpPrototypeExec,
Symbol,
} = primordials;

Expand Down Expand Up @@ -42,6 +43,11 @@ const { URLParse } = require('internal/url');
const kHandle = Symbol('kHandle');
const kDetail = Symbol('kDetail');

// The complete character set of an "${address}:${port}" input. Everything else
// is rejected: delimiters that would introduce a userinfo, path, query, or
// fragment component, and characters the URL parser strips, decodes, or remaps.
const kValidInput = /^[0-9a-fA-FxX.:[\]]+$/;

class SocketAddress {
static isSocketAddress(value) {
return value?.[kHandle] !== undefined;
Expand Down Expand Up @@ -149,6 +155,10 @@ class SocketAddress {
*/
static parse(input) {
validateString(input, 'input');
// The URL parser below silently discards anything that is not the host or
// port, and percent-decodes and IDNA-maps what remains, so restrict the
// input to characters that can appear in an address and port first.
if (RegExpPrototypeExec(kValidInput, input) === null) return;

@Renegade334 Renegade334 Jul 30, 2026

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The only downside is that this matches hostname-like strings like cabbage.ca, which will be parsed by URLParse and returned from this method as "IPv4 addresses".

Should probably also check after parsing that url.hostname passes isIPv4/isIPv6 as appropriate.

@Renegade334 Renegade334 Jul 30, 2026 •
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Or indeed could just validate url.hostname with the simpler /^\[|\.\d+$/ since anything matching those that's not a valid IPv4/IPv6 address would already have been rejected by URLParse.

// While URL.parse is not expected to throw, there are several
// other pieces here that do... the destucturing, the SocketAddress
// constructor, etc. So we wrap this in a try/catch to be safe.
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36 changes: 36 additions & 0 deletions test/parallel/test-socketaddress.js
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Expand Up @@ -162,6 +162,42 @@ describe('net.SocketAddress...', () => {
'abc.123',
'259.1.1.1',
'12:12:12',
// Arbitrary URL components.
'user:80@5.6.7.8',
'user@1.2.3.4',
'1.2.3.4/',
'1.2.3.4/foo',
'1.2.3.4\\foo',
'1.2.3.4?a=b',
'1.2.3.4#frag',
'[1::8]:123/x',
'http://1.2.3.4',
// Whitespace and control characters.
'1.2.3\n.4',
'1.2.3\t.4',
'1.2.3.4\r',
'1.2.3.4 ',
' 1.2.3.4',
'1.2.3.4\x00',
'1.2.3.4\x0b',
'1.2.3.4\x7f',
// Percent-encoding.
'1.2.3.%34',
'1%2E2%2E3%2E4',
'%30%78%66%66%66%66%66%66%66%66',
'1.2.3.%34:8080',
// IDNA.
'１２７.０.０.１',
'０ｘ７ｆ.1',
'1。2。3。4',
'1｡2｡3｡4',
'⑧.0.0.1',
'1.2.3.4\u200b',
'1.2.3.4\ufeff',
'1.2.3.4\u00ad',
'1.2.3.4\u180e',
'1.2.3.4\u2064',
'1.2.3.4\ufe00',
];

bad.forEach((i) => {
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