Executive brief
Adminer, a popular database management tool, unsafely processes the X-Forwarded-Prefix HTTP header without validating the proxy source or prefix value. An attacker can inject an absolute URL into this header to redirect users to attacker-controlled sites after performing database operations, manipulate session cookie scope, or poison self-referential links in the application. While existing authentication prevents the most direct attacks, this creates an open redirect vulnerability and enables session hijacking risks on shared hosting environments.
Technical details
The vulnerability lies in Adminer's reverse-proxy support (bootstrap.inc.php:40-42), which blindly prepends the client-supplied X-Forwarded-Prefix header to $_SERVER["REQUEST_URI"] with no validation or trusted-proxy checking. Because REQUEST_URI always begins with "/", an attacker-supplied prefix like "https://evil.example" creates an absolute URL that flows into three sinks: Location redirect headers (used in db.inc.php, edit.inc.php), the Set-Cookie path attribute via cookie_path() function, and self-referential links. The attack requires network access (spoofable header) but triggers different impacts: authenticated users performing state-changing POSTs (table operations) receive open-redirect responses; unauthenticated attackers can control the session cookie path attribute to enable session-fixation attacks on shared hosts; all users see poisoned self-referential URLs. CR/LF injection is blocked by PHP's header() function, preventing header splitting or XSS. Patched in version 5.5.0.
Affected products
- Vrana Adminer 4.6.0 to 5.4.4
Timeline
- 2026-07-17: disclosed: GHSA-8478-xrj3-h9c2 published on GitHub
- 2026-08-25: other: CVE-2026-34959 published on NVD
- 2026: patched: Fixed in version 5.5.0