CVE-2026-27586
Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, two swallowed errors in `ClientAuthentication.provision()` cause mTLS client certificate authentication to silently fail open when a CA certificate file is missing, unreadable, or malformed. The server starts without error but accepts any client certificate signed by any system-trusted CA, completely bypassing the intended private CA trust boundary. Any deployment using `trusted_ca_cert_file` or `trusted_ca_certs_pem_files` for mTLS will silently degrade to accepting any system-trusted client certificate if the CA file becomes unavailable. This can happen due to a typo in the path, file rotation, corruption, or permission changes. The server gives no indication that mTLS is misconfigured. Version 2.11.1 fixes the vulnerability.
- Score
- CVSS 3.1 9.1 Critical
- Status
- Analyzed - security-advisories@github.com
- Published
- 2026-02-24
- Last modified
- 2026-02-26
- Weaknesses
- CWE-755
Affected products
References
- https://gist.github.com/moscowchill/9566c79c76c0b64c57f8bd0716f97c48
- https://github.com/caddyserver/caddy/releases/tag/v2.11.1
- https://github.com/caddyserver/caddy/security/advisories/GHSA-hffm-g8v7-wrv7
