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 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.

CVSS v4.0

8.7 HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS v3.1

7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

0.60% chance of exploitation in the next 30 days, 46th percentile

Published

2026-07-27

Updated

2026-07-31

Proof-of-concept exploits (2)

• https://tpaidakis.com/writeups/facilio-parser-dos/
• theopaid/Out-of-Bounds-Read-in-facil.io-MIME-Parser-leads-to-Server-Crash0★ · 2026-07-28

References

• CVE Record
• NVD entry

Related

• CVE-2023-27163
• CVE-2026-66730
• CVE-2026-66731
• CVE-2026-66746
• CVE-2026-66748
• CVE-2026-66750