What’s Vulnerable › Vulnerabilities

CVE-2026-66729: facil.io 0.6.0 - 0.7.6 Integer Underflow DoS via Multipart MIME Body Parser

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-27 · updated 2026-10-24
• Weakness: CWE-125

Description

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.

Affected products

• boazsegev facil.io: from 0.6.0 through 0.7.6

References

• https://github.com/theopaid/Out-of-Bounds-Read-in-facil.io-MIME-Parser-leads-to-Server-Crash
• https://tpaidakis.com/writeups/facilio-parser-dos/
• https://www.vulncheck.com/advisories/facil-io-integer-underflow-dos-via-multipart-mime-body-parser

Get alerted when CVE-2026-66729 or the next vulnerability affects your stack