{"id":"CVE-2026-16434","summary":"Adminer before 5.5.1 X-Forwarded-Prefix Backslash Bypass","details":"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.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.","aliases":["GHSA-fr74-9mf9-gf44"],"modified":"2026-08-28T03:30:32.792270004Z","published":"2026-08-25T01:29:57.018Z","database_specific":{"cna_assigner":"VulnCheck","cwe_ids":["CWE-20"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/16xxx/CVE-2026-16434.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/16xxx/CVE-2026-16434.json"},{"type":"ADVISORY","url":"https://github.com/vrana/adminer/security/advisories/GHSA-fr74-9mf9-gf44"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-16434"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/adminer-before-x-forwarded-prefix-backslash-bypass"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/vrana/adminer","events":[{"introduced":"d2ed0f7810e4f05a2fc6348286b622abf6464751"},{"fixed":"be0b989473ec2b929f581234505aed487cbaa5a1"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"5.5.1"},{"introduced":"4.6.0"},{"fixed":"5.5.0"}],"source":["AFFECTED_FIELD","DESCRIPTION"]}}],"versions":["v5.5.0","v5.4.4","v5.4.3","v5.4.2","v5.4.1","v5.4.0","v5.3.0","v5.2.1","v5.2.0","v5.1.1","v5.1.0","v5.0.6","v5.0.5","v5.0.4","v5.0.3","v5.0.2","v5.0.1","v5.0.0","v4.17.1","v4.17.0","v4.16.0","v4.8.1","v4.8.0","v4.7.9","v4.7.8","v4.7.7","v4.7.5","v4.7.4","v4.7.3","v4.7.2","v4.7.1","v4.7.0","v4.6.3","v4.6.2","v4.6.1","v4.6.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-16434.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N"}]}