{"id":"UBUNTU-CVE-2026-27586","details":"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.","modified":"2026-05-20T16:12:13.520555652Z","published":"2026-02-24T17:29:00Z","upstream":["CVE-2026-27586"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-27586"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-27586"},{"type":"REPORT","url":"https://github.com/caddyserver/caddy/security/advisories/GHSA-hffm-g8v7-wrv7"},{"type":"REPORT","url":"https://gist.github.com/moscowchill/9566c79c76c0b64c57f8bd0716f97c48"},{"type":"REPORT","url":"https://github.com/caddyserver/caddy/releases/tag/v2.11.1"}],"affected":[{"package":{"name":"caddy","ecosystem":"Ubuntu:Pro:24.04:LTS","purl":"pkg:deb/ubuntu/caddy?arch=source&distro=esm-apps%2Fnoble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.6.2-6","2.6.2-6ubuntu0.24.04.1","2.6.2-6ubuntu0.24.04.2","2.6.2-6ubuntu0.24.04.2+esm1","2.6.2-6ubuntu0.24.04.3","2.6.2-6ubuntu0.24.04.3+esm1","2.6.2-6ubuntu0.24.04.3+esm2"],"ecosystem_specific":{"binaries":[{"binary_version":"2.6.2-6ubuntu0.24.04.3+esm2","binary_name":"caddy"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-27586.json"}},{"package":{"name":"caddy","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/caddy?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.6.2-9","2.6.2-11","2.6.2-12"],"ecosystem_specific":{"binaries":[{"binary_version":"2.6.2-12","binary_name":"caddy"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-27586.json"}},{"package":{"name":"caddy","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/caddy?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.6.2-12","2.6.2-14"],"ecosystem_specific":{"binaries":[{"binary_version":"2.6.2-14","binary_name":"caddy"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-27586.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"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"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"},{"type":"Ubuntu","score":"medium"}]}