{"schema_version":"1.9.0","id":"CVE-2026-27588","published":"2026-02-24T16:28:28.106Z","modified":"2026-08-12T03:51:35.577623362Z","aliases":["GHSA-x76f-jf84-rqj8","GO-2026-4541"],"related":["SUSE-SU-2026:0757-1","openSUSE-SU-2026:21483-1"],"summary":"Caddy: MatchHost becomes case-sensitive for large host lists (>100), enabling host-based route/auth bypass","details":"Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's HTTP `host` request matcher is documented as case-insensitive, but when configured with a large host list (>100 entries) it becomes case-sensitive due to an optimized matching path. An attacker can bypass host-based routing and any access controls attached to that route by changing the casing of the `Host` header. Version 2.11.1 contains a fix for the issue.","affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/caddyserver/caddy","events":[{"introduced":"551f793700fe1550845c824470b623fd1aa03d36"},{"fixed":"6610e2f1bd8f54853006eefd3849c9965190e57f"}],"database_specific":{"cpe":"cpe:2.3:a:caddyserver:caddy:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"0"},{"fixed":"2.11.1"},{"introduced":"2.10.2"}],"source":["AFFECTED_FIELD","CPE_RANGE","REFERENCES"]}}],"versions":["v2.11.0","v2.11.0-beta.2","v2.11.0-beta.1","v2.10.2"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-27588.json"}}],"references":[{"type":"WEB","url":"https://github.com/caddyserver/caddy/releases/tag/v2.11.1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27588.json"},{"type":"ADVISORY","url":"https://github.com/caddyserver/caddy/security/advisories/GHSA-x76f-jf84-rqj8"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27588"}],"database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-178"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27588.json"},"severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P"}]}