MongoBleed (CVE-2025-14847)

MongoBleed is a high-performance PoC scanner for CVE-2025-14847, a pre-authentication heap memory disclosure vulnerability in the MongoDB C++ Driver. The tool is designed for rapid identification of vulnerable instances across large network ranges.

Technical Analysis

The vulnerability stems from an out-of-bounds (OOB) read in the MongoDB wire protocol’s handling of OP_COMPRESSED messages.

When a server receives an OP_COMPRESSED packet, it relies on the attacker-supplied uncompressedSize field to allocate a buffer for decompression. If the actual decompressed data is significantly smaller than the claimed uncompressedSize, the driver fails to truncate or clear the buffer. As a result, the server returns the entire allocated memory block, which may contain uninitialized heap data, potentially exposing sensitive information such as session tokens, internal pointers, or fragments of other database queries.

Features

• Asynchronous I/O using Python asyncio for high-concurrency scanning
• Precise detection by validating response length against the requested leak size
• Minimal false positives through verified protocol-level interaction
• Automatic logging of vulnerable targets to vulnerable_targets.txt

Installation

git clone https://github.com/Black1hp/mongobleed-scanner/
cd mongobleed-scanner

No external dependencies required (Python Standard Library only).

Usage

Basic usage:

python3 mongobleed.py -i targets.txt

Advanced configuration:

python3 mongobleed.py -i targets.txt -c 100 -t 5

Options

• -i : Input file containing targets (IP, domain, or IP:port)
• -c : Concurrency level (default: 50)
• -t : Connection timeout in seconds (default: 5)

Detection Logic

The scanner identifies vulnerability by exploiting a size mismatch during the BSON decompression phase:

1. The scanner sends a crafted OP_COMPRESSED packet containing a small zlib-compressed payload for example 16-30 bytes .
2. The uncompressedSize field in the packet header is intentionally set to a much larger value (e.g., 64KB).
3. A VULNERABLE state is confirmed if the MongoDB server responds with a MessageLength that aligns with the requested large buffer size rather than the actual decompressed payload size.
4. The server trustfully uses the attacker-provided uncompressedSize to define the response length. Since it fails to update this length with the actual bytes written during decompression, it blindly streams the entire allocated heap buffer—including uninitialized memory—back to the client.
5. The scanner validates the response by reading the extra bytes from the stream, which represent uninitialized fragments of the server's heap memory.

Proof of Concept

MongoBleed_poc.mp4

Note: The video above demonstrates the scanner identifying multiple vulnerable instances and capturing heap fragments in real-time.

Author

Black1hp Security Researcher | Bug Hunter | Red Teamer

• GitHub: https://github.com/black1hp
• X (Twitter): https://x.com/black1hp
• Medium: https://medium.com/@black1hp
• LinkedIn: https://www.linkedin.com/in/black1hp/

Disclaimer

This tool is intended for authorized security testing and research purposes only. The author is not responsible for any unauthorized use or damage resulting from this tool.