CVE-2026-27586 - Caddy's mTLS client authentication silently fails open when CA certificate file ...

CVE ID : CVE-2026-27586 Published : Feb. 24, 2026, 5:29 p.m. | 1 hour, 3 minutes ago Description : 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. Severity: 8.8 | HIGH Visit the link for more details, such as CVSS details, affected products, timeline, and more...