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In Waitress version 1.4.2, a vulnerability exists in the HTTP header parsing logic where a malformed header containing invalid characters (e.g., non-printable bytes) triggers catastrophic backtracking in the regular expression engine. This flaw was introduced when the header validation regex was updated to comply with RFC7230 errata. An attacker can exploit this by sending a single HTTP request with a specially crafted header, causing the process to consume 100% CPU and rendering the service unresponsive.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository demonstrates a Denial of Service (DoS) exploit for Waitress version 1.4.2 (CVE-2020-5236). The exploit leverages a vulnerability in the HTTP header parsing logic, where a header containing invalid characters (such as \x10) causes catastrophic backtracking in a regular expression, resulting in 100% CPU usage and server unresponsiveness. The repository includes a full copy of the Waitress server code (under src/libs/waitress/) and a simple Bottle application (src/server.py) that runs on Waitress. The README provides clear instructions for running the vulnerable server in Docker and for executing the exploit using curl. The main attack vector is a single crafted HTTP request with a malicious header, targeting the running Waitress server on port 8080. The exploit is a proof-of-concept and does not provide post-exploitation capabilities beyond denial of service.
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