CVE-2026-66729: Out-of-bounds Read in boazsegev facil.io
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.
AI Analysis
Technical Summary
CVE-2026-66729 is an integer underflow vulnerability in facil.io's multipart MIME body parser affecting versions 0.6.0 through 0.7.6. The flaw occurs when processing a crafted Content-Disposition header with an empty field name, causing a uint32_t wraparound in http_mime_parser.h. This leads to an out-of-bounds read past the name pointer, resulting in a bus fault that crashes the server process handling the request. The vulnerability requires no authentication and can be triggered remotely via a single POST request.
Potential Impact
Successful exploitation causes a denial of service by crashing the server process handling the HTTP request. There is no indication of code execution or data disclosure from the provided information. The impact is limited to service disruption.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or temporary workaround is currently documented. Until a patch is available, consider restricting or validating incoming multipart POST requests to mitigate potential crashes.
CVE-2026-66729: Out-of-bounds Read in boazsegev facil.io
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.
CVSS v4.0
Score 8.7high
Affected software
boazsegev
facil.io
Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-66729 is an integer underflow vulnerability in facil.io's multipart MIME body parser affecting versions 0.6.0 through 0.7.6. The flaw occurs when processing a crafted Content-Disposition header with an empty field name, causing a uint32_t wraparound in http_mime_parser.h. This leads to an out-of-bounds read past the name pointer, resulting in a bus fault that crashes the server process handling the request. The vulnerability requires no authentication and can be triggered remotely via a single POST request.
Potential Impact
Successful exploitation causes a denial of service by crashing the server process handling the HTTP request. There is no indication of code execution or data disclosure from the provided information. The impact is limited to service disruption.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or temporary workaround is currently documented. Until a patch is available, consider restricting or validating incoming multipart POST requests to mitigate potential crashes.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-07-27T16:27:47.646Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a67906e9c2644c7f885e450
Added to database: 07/27/2026, 17:07:58 UTC
Last enriched: 08/06/2026, 16:36:59 UTC
Last updated: 09/10/2026, 20:02:47 UTC
Views: 84
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.