{"id":"CVE-2026-16434","title":"Adminer 4.6.0 through 5.5.0 (fixed in 5.5.1) contains an incomplete fix for a prior X-Forwarded-Prefix vulnerability (GHSA-8478-xrj3-h9c2)","summary":"Adminer 4.6.0 through 5.5.0 (fixed in 5.5.1) contains an incomplete fix for a prior X-Forwarded-Prefix vulnerability (GHSA-8478-xrj3-h9c2). The validation guard (bootstrap.inc.php) only rejects prefixes matching ^/[^/], blocking //evil.c…","severity":"none","cwe":["CWE-20"],"published":"2026-08-25","updated":"2026-09-08","sourceUpdated":"2026-09-08T20:23:49.880","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-16434","references":[{"url":"https://github.com/vrana/adminer/security/advisories/GHSA-fr74-9mf9-gf44","label":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/adminer-before-x-forwarded-prefix-backslash-bypass","label":"disclosure@vulncheck.com"},{"url":"https://github.com/vrana/adminer/security/advisories/GHSA-fr74-9mf9-gf44","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"tags":["nvd"],"epss":0.00301,"epssPercentile":0.22997,"ingestedAt":"2026-09-08T21:11:12.285Z","slug":"CVE-2026-16434","body":"## Overview\n\nAdminer 4.6.0 through 5.5.0 (fixed in 5.5.1) contains an incomplete fix for a prior X-Forwarded-Prefix vulnerability (GHSA-8478-xrj3-h9c2). The validation guard (bootstrap.inc.php) only rejects prefixes matching ^/[^/], blocking //evil.com but allowing values such as /\\evil.com whose second character is a backslash. Because browsers normalize backslash to forward slash, a network-path reference survives into REQUEST_URI and reaches cookie_path(), affecting the Set-Cookie Path attribute. Exploitation requires that clients can set the X-Forwarded-Prefix header (a misconfigured or absent reverse proxy). Impact is limited to anomalous cookie-path scoping.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}