CVE-2026-27586

CRITICAL

9.1

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.

CVE Details

CVSS v3.1 Score9.1

SeverityCRITICAL

CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Attack VectorNETWORK

ComplexityLOW

Privileges RequiredNONE

User InteractionNONE

Published2/24/2026

Last Modified2/25/2026

Sourcenvd

Honeypot Sightings0

Affected Products

caddyserver:caddy

Weaknesses (CWE)

CWE-755

References

https://gist.github.com/moscowchill/9566c79c76c0b64c57f8bd0716f97c48(security-advisories@github.com)

https://github.com/caddyserver/caddy/releases/tag/v2.11.1(security-advisories@github.com)

https://github.com/caddyserver/caddy/security/advisories/GHSA-hffm-g8v7-wrv7(security-advisories@github.com)

IOC Correlations

No correlations recorded

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