CVE-2026-66731
Public exploit code is available. Proof-of-concept or working exploit code for CVE-2026-66731 is indexed in GitHub PoC. Expect opportunistic scanning and exploitation attempts — prioritize remediation even though it is not (yet) in the CISA KEV catalog.
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.
⚡ Watch CVE-2026-66731
Get an email if CVE-2026-66731 is added to CISA KEV, gains public exploit code, or a new advisory cites it — max one per day, one-click unsubscribe.
Exploitation outlook
- Low exploitation risk0.47% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 38% of all EPSS-scored CVEs.
Exploit availability
Public exploit or proof-of-concept code for CVE-2026-66731 is indexed in these free datasets. Available exploit code raises real-world risk independent of the CVSS score.
- GitHub PoCPublic proof-of-concept repositories on GitHub reference this CVE.look it up ↗
Advisory coverage (1)
External references
Embed the live status
— this badge updates automatically when the KEV or exploit status changes. How to embed it →
[](https://www.csirts.com/cve/CVE-2026-66731)