CVE-2026-21857 Redaxo has Path Traversal in Backup Addon Leading to Arbitrary File Read
Authenticated users with backup permissions can read arbitrary files within the webroot via path traversal in the Redaxo Backup addon.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-21857?
CVE-2026-21857 is a high-severity path traversal vulnerability in redaxo, published on 7 Jan 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Official description
REDAXO is a PHP-based content management system. Prior to version 5.20.2, authenticated users with backup permissions can read arbitrary files within the webroot via path traversal in the Backup addon's file export functionality. The Backup addon does not validate the `EXPDIR` POST parameter against the UI-generated allowlist of permitted directories. An attacker can supply relative paths containing `../` sequences (or even absolute paths inside the document root) to include any readable file in the generated `.tar.gz` archive. Version 5.20.2 fixes this issue.
Which versions are affected by CVE-2026-21857?
2 open source packages ship an affected version, including redaxo/source. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
redaxo/source Packagist | All versions | 5.20.2 |
redaxo/source Packagist | All versions | 5.20.2 |
Products include Redaxo Redaxo.
How do I fix CVE-2026-21857?
Upgrade redaxo/source to 5.20.2 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-21857 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-21857 exists.
Public exploit code: 1 proofs of concept on GitHub.
Other vulnerabilities in redaxo
Sources
Also known as GHSA-824x-88xg-cwrv.