PatchSiren cyber security CVE debrief
CVE-2026-66730 boazsegev CVE debrief
CVE-2026-66730 is a denial-of-service vulnerability in facil.io versions 0.6.0 through 0.7.6. The vulnerability is located in the multipart body parser and allows an unauthenticated remote attacker to permanently freeze worker processes at 100% CPU by sending a multipart/form-data request with a partial closing boundary. The missing progress guard in the parser loop causes http_mime_parse to return 0 bytes consumed without setting done or error flags, causing the calling loop to re-invoke the parser on the same buffer indefinitely, exhausting all workers and permanently disabling the server until manually restarted.
- Vendor
- boazsegev
- Product
- facil.io
- CVSS
- HIGH 8.7
- CISA KEV
- Not listed in stored evidence
- Original CVE published
- 2026-07-27
- Original CVE updated
- 2026-07-27
- Advisory published
- 2026-07-27
- Advisory updated
- 2026-07-27
Who should care
Users of facil.io versions 0.6.0 through 0.7.6 should be aware of this vulnerability and take steps to mitigate it. This vulnerability has a high CVSS score of 8.7, indicating a high level of severity.
Technical summary
The vulnerability is caused by a missing progress guard in the parser loop of the multipart body parser in facil.io. This causes the http_mime_parse function to return 0 bytes consumed without setting the done or error flags, leading to an infinite loop that exhausts all workers and permanently disables the server. An unauthenticated remote attacker can exploit this vulnerability by sending a specially crafted multipart/form-data request with a partial closing boundary.
Defensive priority
High
Recommended defensive actions
- Apply the vendor's patch or upgrade to a version of facil.io that is not vulnerable.
- Implement compensating controls, such as rate limiting or IP blocking, to prevent exploitation.
- Monitor server resources and worker processes for signs of exhaustion.
- Consider implementing additional security measures, such as authentication or input validation, to prevent similar attacks.
- Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.
- Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
- Track exceptions, retest remediated assets, and close the item only after evidence is documented.
Evidence notes
The CVE record was published on 2026-07-27T17:16:42.660Z and was last modified on 2026-07-27T19:17:23.350Z. The NVD entry is currently Received. The vulnerability has a CVSS score of 8.7 and a severity of HIGH.
Official resources
AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-07-27T17:16:42.660Z and has not been modified since then. The NVD entry is currently Received.