What is the CVSS score of CVE-2026-27586?

CVE-2026-27586 has a CVSS 3.1 base score of 9.1 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N. EPSS exploitation probability: 0.1%.

Which versions of TLS are affected by CVE-2026-27586?

Caddy servers prior to version 2.11.1 fail silently when mutual TLS (mTLS) client certificate validation encounters errors, allowing unauthorized clients to bypass authentication entirely.. A patch is available.

Is there a public PoC exploit available for CVE-2026-27586?

Yes, a public proof-of-concept exploit is available for CVE-2026-27586. Prioritise patching immediately. EPSS: 0.1%.

TLS CVE-2026-27586

CRITICAL

Improper Handling of Exceptional Conditions (CWE-755)

2026-02-24 security-advisories@github.com

GHSA-hffm-g8v7-wrv7

TLS Caddy Suse

9.1

CVSS 3.1

CVSS VectorNVD

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

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

DescriptionNVD

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.

AnalysisAI

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. …

RemediationAI

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. …

Analysis

Detailed AI-generated intelligence summary covering attack vector, impact assessment, affected versions, remediation steps, and indicators of compromise.

POChttps://••••••••••.com/exploit

PATCHhttps://••••••••••.com/patch

ADVISORYhttps://••••••••••.com/advisory

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CVE-2026-27586 vulnerability details – vuln.today

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TLS CVE-2026-27586

CVSS VectorNVD

Lifecycle Timeline

DescriptionNVD

AnalysisAI

RemediationAI

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External POC / Exploit Code