{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-27586","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","state":"PUBLISHED","assignerShortName":"GitHub_M","dateReserved":"2026-02-20T17:40:28.450Z","datePublished":"2026-02-24T16:08:20.569Z","dateUpdated":"2026-02-26T20:56:20.526Z"},"containers":{"cna":{"title":"Caddy's mTLS client authentication silently fails open when CA certificate file is missing or malformed","problemTypes":[{"descriptions":[{"cweId":"CWE-755","lang":"en","description":"CWE-755: Improper Handling of Exceptional Conditions","type":"CWE"}]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"HIGH","vulnIntegrityImpact":"HIGH","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":8.8,"baseSeverity":"HIGH","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:P","version":"4.0"}}],"references":[{"name":"https://github.com/caddyserver/caddy/security/advisories/GHSA-hffm-g8v7-wrv7","tags":["x_refsource_CONFIRM"],"url":"https://github.com/caddyserver/caddy/security/advisories/GHSA-hffm-g8v7-wrv7"},{"name":"https://gist.github.com/moscowchill/9566c79c76c0b64c57f8bd0716f97c48","tags":["x_refsource_MISC"],"url":"https://gist.github.com/moscowchill/9566c79c76c0b64c57f8bd0716f97c48"},{"name":"https://github.com/caddyserver/caddy/releases/tag/v2.11.1","tags":["x_refsource_MISC"],"url":"https://github.com/caddyserver/caddy/releases/tag/v2.11.1"}],"affected":[{"vendor":"caddyserver","product":"caddy","versions":[{"version":"< 2.11.1","status":"affected"}]}],"providerMetadata":{"orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M","dateUpdated":"2026-02-24T16:08:20.569Z"},"descriptions":[{"lang":"en","value":"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."}],"source":{"advisory":"GHSA-hffm-g8v7-wrv7","discovery":"UNKNOWN"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-02-26T20:55:27.670740Z","id":"CVE-2026-27586","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-02-26T20:56:20.526Z"}}]}}