CVE-2026-27586

9.1 CRITICAL
Published: February 24, 2026 Modified: February 25, 2026
View on NVD

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.

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CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
https://gist.github.com/moscowchill/9566c79c76c0b64c57f8bd0716f97c48
Source: security-advisories@github.com
Exploit
https://github.com/caddyserver/caddy/releases/tag/v2.11.1
Source: security-advisories@github.com
Release Notes
https://github.com/caddyserver/caddy/security/advisories/GHSA-hffm-g8v7-wrv7
Source: security-advisories@github.com
Exploit Vendor Advisory

3 reference(s) from NVD

Quick Stats

CVSS v3 Score
9.1 / 10.0
EPSS (Exploit Probability)
0.1%
24th percentile
Exploitation Status
Not in CISA KEV

Weaknesses (CWE)

Affected Vendors

caddyserver