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Vulnerabilities

Vulnerability · CVE-2026-27586

Caddy is an extensible server platform that uses TLS by default.

Published Feb 24, 2026 · catalog updated Jun 17, 2026 · Caddy is an extensible

Check if you run it

No confirmed exploitation is on record for CVE-2026-27586. EPSS is 0.40%. Act only if a listed version of Caddy is an extensible is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Caddy is an extensible).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High8.8
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.40%
Remediation
Advisory link
Affected products
cpe caddyserver/caddy

Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, two swallowed errors in 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 or 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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe caddyserver/caddyversion unspecified

How to fix CVE-2026-27586

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-27586. EPSS is 0.40%. Act only if a listed version of Caddy is an extensible is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-755: Improper Handling of Exceptional Conditions. EPSS 0.40%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Feb 24, 2026 · NIST NVD

    Detected

    Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, two swallowed errors in 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 bou

  2. Jun 17, 2026 · NIST NVD

    Updated

    Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, two swallowed errors in 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 bou

Sources

  • CVE.orgVulnerability recordCVE-2026-27586

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-27586

    30-day exploitation probability 0.4%

    first.org
  • NIST NVDVulnerability recordCVE-2026-27586

    Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, two swallowed errors in cause mTLS client certificate authentication to silently fail open when a CA certificate file is missing, unreadable, or malformed.

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.