CVE-2026-27586
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.
How to fix
- caddyserver caddy2.11.1 or later
- github.com/caddyserver/caddy/v22.11.1 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| caddyserver caddy | v < 2.11.1 | 2.11.1 |
| github.com/caddyserver/caddy/v2Go | v < 2.11.1 | 2.11.1 |
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