{"id":"CVE-2026-52845","sourceIdentifier":"security-advisories@github.com","published":"2026-06-23T18:18:05.267","lastModified":"2026-07-15T01:16:22.240","vulnStatus":"Modified","cveTags":[],"descriptions":[{"lang":"en","value":"Caddy is an extensible server platform that uses TLS by default. Prior to 2.11.4, forward_auth copy_headers deletes the exact client-supplied identity header before copying the trusted value from the auth gateway. But when the request later goes through php_fastcgi, Caddy normalizes HTTP headers into CGI variables by replacing - with _. This lets a client send an underscore alias that survives the forward_auth delete step but becomes the same PHP/FastCGI variable. Result: a remote client can inject or sometimes override identity/group headers trusted by PHP/FastCGI applications behind Caddy. This vulnerability is fixed in 2.11.4."}],"affected":[{"source":"security-advisories@github.com","affectedData":[{"vendor":"caddyserver","product":"caddy","versions":[{"version":"< 2.11.4","status":"affected"}]}]},{"source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c","affectedData":[{"vendor":"Red Hat","product":"Red Hat Hardened Images","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","packageName":"caddy","cpes":["cpe:/a:redhat:hummingbird:1"]}]}],"metrics":{"cvssMetricV31":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N","baseScore":8.1,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"NONE"},"exploitabilityScore":2.8,"impactScore":5.2},{"source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N","baseScore":8.1,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"NONE"},"exploitabilityScore":2.8,"impactScore":5.2}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-06-24T14:25:18.472130Z","id":"CVE-2026-52845","options":[{"exploitation":"poc"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"weaknesses":[{"source":"security-advisories@github.com","type":"Secondary","description":[{"lang":"en","value":"CWE-287"},{"lang":"en","value":"CWE-290"},{"lang":"en","value":"CWE-444"}]},{"source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c","type":"Secondary","description":[{"lang":"en","value":"CWE-444"}]}],"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:caddyserver:caddy:*:*:*:*:*:*:*:*","versionEndExcluding":"2.11.4","matchCriteriaId":"6CC2FFA3-3F35-452A-A0B6-C1B66C0C73E6"}]}]}],"references":[{"url":"https://github.com/caddyserver/caddy/security/advisories/GHSA-f59h-q822-g45g","source":"security-advisories@github.com","tags":["Exploit","Third Party Advisory"]},{"url":"https://access.redhat.com/security/cve/CVE-2026-52845","source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2491907","source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"},{"url":"https://github.com/caddyserver/caddy/security/advisories/GHSA-f59h-q822-g45g","source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","tags":["Exploit","Third Party Advisory"]},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52845.json","source":"0b0ca135-0b70-47e7-9f44-1890c2a1c46c"}]}