Vulnerability Description
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.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/theopaid/Negative-Chunk-Size-Parsing-Causes-Memory-Corruption
- https://tpaidakis.com/writeups/facilio-parser-dos/
- https://www.vulncheck.com/advisories/facil-io-http-chunked-transfer-encoding-par
FAQ
What is CVE-2026-66731?
CVE-2026-66731 is a vulnerability with a CVSS score of 7.5 (HIGH). 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 n...
How severe is CVE-2026-66731?
CVE-2026-66731 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-66731?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.