CVE-2026-66729: facil.io 0.6.0 through 0.7.6 contains an integer underflow vulnerability in the multipart MIME body parser that allows unauthenticated remote attackers to crash the server process
facil.io 0.6.0 through 0.7.6 contains an integer underflow vulnerability in the multipart MIME body parser that allows unauthenticated remote attackers to crash the server process by sending a crafted Content-Disposition header with an empty field name. Attackers can trigger a uint32_t wraparound in http_mime_parser.h causing an out-of-bounds memory read past the name pointer, resulting in a bus fault that crashes the handling worker with a single POST request.
Details
Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-66729
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-667290.60% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 45% of all scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-66729 | coverage & exploitation status | NVD · CVE.org |
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