{"id":"CVE-2026-16434","aliases":["DEBIAN-CVE-2026-16434","EUVD-2026-65195","GHSA-fr74-9mf9-gf44","GHSA-jh7j-hfxx-jv6m","UBUNTU-CVE-2026-16434"],"status":"published","title":"Adminer before 5.5.1 X-Forwarded-Prefix Backslash Bypass","description":"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.","severity":{"version":"4.0","score":2.3,"vector":"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","level":"low","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00389,"percentile":0.33359,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-20"],"published":"2026-08-25T01:29:57Z","modified":"2026-10-28T02:30:44Z","fixes":[{"ecosystem":"Debian:14","package":"adminer","fixed_in":["6.0.0-1"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Debian:12","package":"adminer","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.8.1-1","4.8.1-2","4.8.1-4","5.1.0-1","5.2.1+dfsg-1","5.3.0+dfsg-1","5.4.0+dfsg-1","5.4.1+dfsg-1","5.4.2+dfsg-1","5.4.3+dfsg-1","5.4.4+dfsg-1","6.0.0-1","6.0.1-1","6.0.2-1","6.1.0-1","6.1.1-1","6.1.2-1"]},{"source":"osv","ecosystem":"Debian:13","package":"adminer","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.2.1+dfsg-1","5.3.0+dfsg-1","5.4.0+dfsg-1","5.4.1+dfsg-1","5.4.2+dfsg-1","5.4.3+dfsg-1","5.4.4+dfsg-1","6.0.0-1","6.0.1-1","6.0.2-1","6.1.0-1","6.1.1-1","6.1.2-1"]},{"source":"osv","ecosystem":"Debian:14","package":"adminer","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.0.0-1"}]}],"versions":["5.2.1+dfsg-1","5.3.0+dfsg-1","5.4.0+dfsg-1","5.4.1+dfsg-1","5.4.2+dfsg-1","5.4.3+dfsg-1","5.4.4+dfsg-1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:16.04:LTS","package":"adminer","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.2.1-1","4.2.1-1ubuntu1","4.2.1-1ubuntu1+esm1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:18.04:LTS","package":"adminer","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.3.1-2","4.5.0-1","4.6.1-1","4.6.2-1","4.6.2-1ubuntu0.1~esm1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:20.04:LTS","package":"adminer","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.7.2-1","4.7.4-1","4.7.5-1","4.7.6-1","4.7.6-1ubuntu0.1~esm1"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"adminer","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.7.9-2","4.8.1-1"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"adminer","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.8.1-1","4.8.1-1ubuntu1","4.8.1-2"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"adminer","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.2.1+dfsg-1","5.3.0+dfsg-1","5.4.0+dfsg-1","5.4.1+dfsg-1"]}],"products":[{"vendor":"vrana","product":"adminer"}],"references":[{"url":"https://github.com/vrana/adminer/security/advisories/GHSA-fr74-9mf9-gf44","tags":["vendor-advisory","exploit","advisory","report"]},{"url":"https://www.vulncheck.com/advisories/adminer-before-x-forwarded-prefix-backslash-bypass","tags":["third-party-advisory","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-16434","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-jh7j-hfxx-jv6m"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/16xxx/CVE-2026-16434.json","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-16434","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-16434","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-16434","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-16434","title":"Adminer before 5.5.1 X-Forwarded-Prefix Backslash Bypass","description":"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.","status":"published","published":"2026-08-25T01:29:57.018Z","modified":"2026-08-27T14:34:04.155Z","cvss":[{"version":"4.0","score":2.3,"vector":"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","level":"low","assessor":"cna"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T14:20:11.24076Z"}],"euvd":[{"id":"EUVD-2026-65195","description":"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.","status":"published","published":"2026-08-25T01:29:57Z","modified":"2026-08-27T14:34:04Z","cvss":[{"version":"4.0","score":2.3,"vector":"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","level":"low"}],"updated_at":"2026-11-02T18:01:28.115205Z"}],"ghsa":[{"id":"GHSA-jh7j-hfxx-jv6m","title":"Adminer 4.6.0 through 5.5.0 (fixed in 5.5.1) contains an incomplete fix for a prior X-Forwarded...","description":"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.","status":"published","published":"2026-08-25T03:32:08Z","modified":"2026-08-25T03:32:14Z","cvss":[{"version":"4.0","score":2.3,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"low"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T15:10:55.456762Z"}],"nvd":[{"id":"CVE-2026-16434","description":"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.","status":"published","published":"2026-08-25T02:16:40.11Z","modified":"2026-10-12T15:10:00.207Z","cvss":[{"version":"4.0","score":2.3,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"low","assessor":"secondary"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T14:12:41.018848Z"}],"osv":[{"id":"CVE-2026-16434","title":"Adminer before 5.5.1 X-Forwarded-Prefix Backslash Bypass","description":"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.","status":"published","published":"2026-08-25T01:29:57.018Z","modified":"2026-10-28T02:30:44.119868334Z","cvss":[{"version":"4.0","score":2.3,"vector":"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","level":"low"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T15:44:57.682091Z"},{"id":"DEBIAN-CVE-2026-16434","description":"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.","status":"published","published":"2026-08-25T02:16:40.11Z","modified":"2026-10-13T10:00:10.418276705Z","cvss":[{"version":"4.0","score":2.3,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"low"}],"updated_at":"2026-11-02T15:45:52.562592Z"},{"id":"UBUNTU-CVE-2026-16434","description":"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.","status":"published","published":"2026-08-25T02:16:00Z","modified":"2026-09-02T19:35:29.83549199Z","cvss":[{"version":"4.0","score":2.3,"vector":"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","level":"low"}],"updated_at":"2026-11-02T16:56:00.592716Z"}]}}