CVE-2026-27586
February 24, 2026
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.
Affected Packages
github.com/caddyserver/caddy (GO):
Affected version(s) >=v0.5.0 <v2.11.1Fix Suggestion:
Update to version v2.11.1Related Resources (7)
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Contact UsCVSS v4
Base Score:
8.8
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
HIGH
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
Exploit Maturity
POC
CVSS v3
Base Score:
9.1
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
NONE
Weakness Type (CWE)
Improper Handling of Exceptional Conditions
EPSS
Base Score:
0.08
