Bug 2442407 (CVE-2026-27586) - CVE-2026-27586 github.com/caddyserver/caddy/v2/modules/caddytls: Caddy: Authentication bypass via mTLS client certificate validation failure
Summary: CVE-2026-27586 github.com/caddyserver/caddy/v2/modules/caddytls: Caddy: Authe...
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Status: NEW
Alias: CVE-2026-27586
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security DevOps Team
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Depends On: 2442430 2442431 2442432 2442433
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-02-24 17:04 UTC by OSIDB Bzimport
Modified: 2026-02-24 19:21 UTC (History)
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Description OSIDB Bzimport 2026-02-24 17:04:56 UTC 
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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