# CVE-2026-34959: Adminer before 5.5.0 Open Redirect via X-Forwarded-Prefix

> Attackers can exploit unvalidated X-Forwarded-Prefix headers to redirect users to malicious sites or manipulate session cookies in Adminer.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 25 Aug 2026
- **Updated:** 26 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-34959, GHSA-8478-xrj3-h9c2, GHSA-fh9x-8h7v-rwhv, UBUNTU-CVE-2026-34959

## What is CVE-2026-34959?

CVE-2026-34959 is a medium-severity vulnerability in vrana adminer, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

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.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-34959?


## How do I fix CVE-2026-34959?

Upgrade to a fixed version.

## Is CVE-2026-34959 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34959 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-34959 and fix it if it is affected.

What it is: CVE-2026-34959 is a medium-severity vulnerability in vrana adminer, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34959 exists.

Affected product: vrana adminer. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-34959/ (Markdown: https://insights.sbomify.com/CVE-2026-34959/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-34959
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-34959
- OSV: https://osv.dev/vulnerability/CVE-2026-34959

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-34959/
Summaries are generated and may contain mistakes; the official description above is the record.