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CVE-2025-23167 is an HTTP request-smuggling vulnerability in the Node.js 20 HTTP parser. The parser incorrectly accepts an HTTP/1 header-section terminator formed as carriage return, line feed, carriage return, followed by a non-line-feed character, rather than requiring the valid carriage return, line feed, carriage return, line feed sequence. This can cause Node.js and an intermediary such as a reverse proxy to interpret request boundaries differently. The issue is resolved by upgrading llhttp to version 9, which strictly enforces valid HTTP header termination.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository provides a working proof-of-concept exploit for CVE-2025-23167, a request smuggling vulnerability in Node.js 20.x versions prior to v20.19.2. The repository contains three files: a README.md with usage instructions, exploit.py (the main exploit script), and lab.js (a Node.js Express server to simulate a vulnerable environment). The exploit.py script crafts a specially malformed HTTP request to the target server, attempting to smuggle a second request by exploiting improper header termination. If the target is vulnerable, the script detects multiple HTTP responses, indicating successful exploitation. The lab.js file sets up a local Express server on http://localhost:8989 for testing. The exploit targets any Node.js HTTP server running the affected versions and is network-based, requiring only TCP/IP access to the target's HTTP port.
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