---
id: CVE-2026-34959
title: >-
  Adminer 4.6.0 before 5.5.0 prepends the client-supplied X-Forwarded-Prefix
  header to $_SERVER["REQUEST_URI"] with no trusted-proxy check and no
  validation of the prefix value
summary: >-
  Adminer 4.6.0 before 5.5.0 prepends the client-supplied X-Forwarded-Prefix
  header to $_SERVER["REQUEST_URI"] with no trusted-proxy check and no
  validation of the prefix value. An attacker can supply an absolute URL (e.g.
  X-Forwarded-Pref…
severity: medium
cvss: 4.7
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N'
cwe:
  - CWE-20
published: '2026-08-25'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T20:23:49.880'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-34959'
references:
  - url: 'https://github.com/vrana/adminer/security/advisories/GHSA-8478-xrj3-h9c2'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/adminer-before-open-redirect-via-x-forwarded-prefix
    label: disclosure@vulncheck.com
  - url: 'https://github.com/vrana/adminer/security/advisories/GHSA-8478-xrj3-h9c2'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
epss: 0.0029
epssPercentile: 0.19257
ingestedAt: '2026-09-08T21:11:12.285Z'
---

## Overview

Adminer 4.6.0 before 5.5.0 prepends the client-supplied X-Forwarded-Prefix header to $_SERVER["REQUEST_URI"] with no trusted-proxy check and no validation of the prefix value. An attacker can supply an absolute URL (e.g. X-Forwarded-Prefix: https://evil.example) that flows into Location redirect headers, the Set-Cookie path attribute, and self-referential links. This enables an authenticated open redirect after state-changing POSTs, unauthenticated control of the session cookie path attribute, and poisoning of self-referential links; CR/LF cannot be injected, so header splitting/XSS is not possible.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.