CVE-2026-66731

EIP tracks 1 public exploit for CVE-2026-66731. PoCs published by theopaid.

AI-analyzed exploit summary This repository provides a detailed technical analysis of CVE-2026-66731, a memory corruption vulnerability in facil.io's HTTP/1.1 parser caused by improper handling of negative chunk sizes in chunked transfer encoding. The flaw leads to a server crash due to an out-of-bounds read when the parser computes a pointer 16MB before the input buffer.

facil.io 0.7.5 through 0.7.6 contains a denial-of-service vulnerability in the HTTP/1.1 chunked transfer encoding parser that allows unauthenticated remote attackers to crash the server by sending a negative chunk size value. Attackers can send a single POST request with a Transfer-Encoding: chunked header containing a leading minus sign in the chunk size field, causing the parser in http1_parser.h to compute a large positive integer from the negated value, corrupting internal state and moving the read pointer into unmapped memory resulting in a fault.