PatchTheCVECVE-2026-66729: facil.io 0.6.0 through 0.7.6 contains an integer underflow vulnerability in the multipart MIME body parser tha
CVE-2026-66729 is a high-severity flaw (CVSS 7.5) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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 singl
Why this priority
- High severity
- CISA SSVC: public proof of concept
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 7.5 (High) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.8% (top 44%) |
| CISA exploited list | No |
| Weakness | CWE-125 |
| Published | 2026-07-27 |
| Last modified | 2026-10-24 |
Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Timeline
- Published CVE record published
- Updated Record last modified
Exact fixes by distribution
Public exploits and detection
Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.
- GitHub PoC: theopaid/CVE-2026-66729-Out-of-Bounds-Read-in-facil.io-MIME-Parser-leads-to-Server-Crash (1 stars)
- Write-up: github.com/theopaid/Out-of-Bounds-Read-in-facil.io-MIME-Parser-leads-to-Server-Crash
- Write-up: tpaidakis.com/writeups/facilio-parser-dos/
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-66729?
No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.
Is CVE-2026-66729 being exploited?
CVE-2026-66729 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-66729 affect?
CVE-2026-66729 affects affected software. Severity is high (CVSS 7.5). 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 empt
How urgent is CVE-2026-66729?
Priority 48/100. High severity; CISA SSVC: public proof of concept; Remotely exploitable, no login, no user action