Vulnerability 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.
Related Weaknesses (CWE)
References
- https://github.com/vrana/adminer/security/advisories/GHSA-fr74-9mf9-gf44
- https://www.vulncheck.com/advisories/adminer-before-x-forwarded-prefix-backslash
- https://github.com/vrana/adminer/security/advisories/GHSA-fr74-9mf9-gf44
FAQ
What is CVE-2026-16434?
CVE-2026-16434 is a documented vulnerability. 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 prefix...
How severe is CVE-2026-16434?
CVSS scoring is not yet available for CVE-2026-16434. Check NVD for updates.
Is there a patch for CVE-2026-16434?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.