Redaxo has Path Traversal in Backup Addon Leading to Arbitrary File Read

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:N · score source

EPSS

• CVE-2026-21857: 0.53% estimated exploitation activity in the next 30 days; percentile 45.22 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Authenticated users with backup permissions can read arbitrary files within the webroot via path traversal in the Backup addon's file export functionality. <img width="664" height="899" alt="image" src="https://github.com/user-attachments/assets/fd1ca69e-b275-4daf-9a62-621cde6525f5" / <img width="2358" height="445" alt="image" src="https://github.com/user-attachments/assets/fad81152-9e1b-413e-9823-09540a23e2fb" / Details 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. Vulnerable code: - redaxo/src/addons/backup/pages/export.php (lines 72-76) – directly uses $POST['EXPDIR'] - redaxo/src/addons/backup/lib/backup.php (lines ~413 & ~427) – concatenates unsanitized user input with base path This allows disclosure of sensitive files…

Published by the source

5 Jan 2026, 20:02 UTC

Last modified by the source

8 Jan 2026, 20:07 UTC

Source last checked

26 Oct 2026, 14:35 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-824x-88xg-cwrv

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# Patch Next advisory brief: CVE-2026-21857

Advisory: Redaxo has Path Traversal in Backup Addon Leading to Arbitrary File Read
IDs: CVE-2026-21857, GHSA-824x-88xg-cwrv
Record: https://patchnext.com/advisories/cve-2026-21857 (revision 1, source checked 26 Oct 2026, 14:35 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: redaxo/source 5.20.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist redaxo/source: affected <= 5.20.1; fixed in 5.20.2

## Suggested inspection (read-only)
- Packagist redaxo/source: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on redaxo/source.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-824x-88xg-cwrv (GitHub-reviewed advisory GHSA-824x-88xg-cwrv lists affected ranges: Packagist redaxo/source >=0 <=5.20.1)

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