{"cve":"CVE-2026-27588","nvd":{"published":"2026-02-24T17:29:04.163","modified":"2026-06-17T10:27:21.117","status":"Analyzed","description":"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.","cvss_v4":{"vector":"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","score":7.7},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","score":9.1},"cwes":["CWE-178"],"references":["https://github.com/caddyserver/caddy/releases/tag/v2.11.1","https://github.com/caddyserver/caddy/security/advisories/GHSA-x76f-jf84-rqj8"],"products":["caddyserver:caddy"],"source":"nvd","synced_at":"2026-10-19T22:24:17.937441719+00:00"},"epss":{"cve":"CVE-2026-27588","score":0.00425,"percentile":0.36777,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-x76f-jf84-rqj8","url":"https://osv.dev/vulnerability/GHSA-x76f-jf84-rqj8","summary":"Caddy: MatchHost becomes case-sensitive for large host lists (>100), enabling host-based route/auth bypass","modified":"2026-02-27T19:53:54Z","packages":[{"ecosystem":"Go","name":"github.com/caddyserver/caddy/v2","purl":"pkg:golang/github.com/caddyserver/caddy/v2","ranges":["<2.11.1"],"fixed":["2.11.1"]}]},{"id":"GO-2026-4541","url":"https://osv.dev/vulnerability/GO-2026-4541","summary":"Caddy MatchHost becomes case-sensitive in github.com/caddyserver/caddy/v2","modified":"2026-02-26T19:26:02.034387Z","packages":[{"ecosystem":"Go","name":"github.com/caddyserver/caddy/v2","purl":"pkg:golang/github.com/caddyserver/caddy/v2","ranges":["<2.11.1"],"fixed":["2.11.1"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}