{"id":"CVE-2026-16434","state":"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.","publishedAt":"2026-08-25T01:29:57.018Z","updatedAt":"2026-08-27T14:34:04.155Z","severity":{"score":2.3,"label":"Low","version":"4.0","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","source":"VulnCheck"},"assigner":"VulnCheck","products":["vrana adminer"],"affected":[{"vendor":"vrana","product":"adminer","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"5.5.1","versionType":"semver"},{"version":"5.5.1","status":"unaffected","versionType":"semver"}]}],"references":["https://github.com/vrana/adminer/security/advisories/GHSA-fr74-9mf9-gf44","https://www.vulncheck.com/advisories/adminer-before-x-forwarded-prefix-backslash-bypass"],"weaknesses":["CWE-20"],"ingestedAt":"2026-10-29T20:11:00.674Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/16xxx/CVE-2026-16434.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-16434","state":"PUBLISHED","datePublished":"2026-08-25T01:29:57.018Z","dateUpdated":"2026-08-27T14:34:04.155Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-07-21T01:28:32.813Z"},"containers":{"cna":{"title":"Adminer before 5.5.1 X-Forwarded-Prefix Backslash Bypass","descriptions":[{"lang":"en","value":"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). 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Impact is limited to anomalous cookie-path scoping."}],"affected":[{"vendor":"vrana","product":"adminer","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"5.5.1","versionType":"semver"},{"version":"5.5.1","status":"unaffected","versionType":"semver"}]}],"references":[{"url":"https://github.com/vrana/adminer/security/advisories/GHSA-fr74-9mf9-gf44","tags":["vendor-advisory"],"name":"GitHub Security Advisory (GHSA-fr74-9mf9-gf44)"},{"url":"https://www.vulncheck.com/advisories/adminer-before-x-forwarded-prefix-backslash-bypass","name":"VulnCheck Advisory: Adminer before 5.5.1 X-Forwarded-Prefix Backslash Bypass","tags":["third-party-advisory"]}],"metrics":[{"format":"CVSS","cvssV4_0":{"version":"4.0","vectorString":"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","attackVector":"NETWORK","attackComplexity":"HIGH","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"PASSIVE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"LOW","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":2.3,"baseSeverity":"LOW"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-20","lang":"en","description":"Improper Input Validation","type":"CWE"}]}],"providerMetadata":{"shortName":"VulnCheck","orgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateUpdated":"2026-08-25T01:29:57.018Z"},"datePublic":"2026-07-21T00:00:00.000Z","cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:adminer:adminer:*:*:*:*:*:*:*:*","versionEndExcluding":"5.5.1"}]}]}],"credits":[{"lang":"en","value":"Infinit3i","type":"reporter"}],"x_generator":{"engine":"vulncheck-endgame"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/vrana/adminer/security/advisories/GHSA-fr74-9mf9-gf44","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-27T14:31:46.966890Z","id":"CVE-2026-16434","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-27T14:34:04.155Z"}}]}}}