CVE-2026-27586

CRITICAL
2026-02-24 [email protected] GHSA-hffm-g8v7-wrv7
9.1
CVSS 3.1
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CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

Lifecycle Timeline

4
Patch Released
Mar 31, 2026 - 21:13 nvd
Patch available
Analysis Generated
Mar 12, 2026 - 21:55 vuln.today
PoC Detected
Feb 25, 2026 - 17:14 vuln.today
Public exploit code
CVE Published
Feb 24, 2026 - 17:29 nvd
CRITICAL 9.1

Tags

Tls Caddy Suse

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.

Analysis

TLS error swallowing in Caddy web server before 2.11.1 allows bypassing client certificate authentication. Errors in ClientCAs handling are silenced, potentially accepting invalid client certificates. …

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Remediation

Within 24 hours: Inventory all Caddy deployments and document versions; audit CA certificate files for missing or corrupted entries; enable detailed logging of authentication failures. Within 7 days: Test upgrade path to Caddy 2.11.1 or later in non-production environments; validate mTLS handshake logs to confirm authentication is enforced. …

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Priority Score

66
Low Medium High Critical
KEV: 0
EPSS: +0.1
CVSS: +46
POC: +20

Vendor Status

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CVE-2026-27586 vulnerability details – vuln.today
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