CVE-2026-16434
Adminer before 5.5.1 X-Forwarded-Prefix Backslash Bypass
- State
- Published
- Severity
- 2.3 Low
- Published
- Aug 25, 2026
- Updated
- Aug 27, 2026
- Reserved
- Jul 21, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 2.3 Low | 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 | VulnCheck |
Weaknesses
- CWE-20 Improper Input Validation
Affected Products
| Product | Versions |
|---|---|
adminervrana |
|
References
- GitHub Security Advisory (GHSA-fr74-9mf9-gf44)vendor-advisory
- VulnCheck Advisory: Adminer before 5.5.1 X-Forwarded-Prefix Backslash Bypassthird-party-advisory
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