CVE-2026-21857

Redaxo Backup Path Traversal: Archiving the Crown Jewels

Amit Schendel
Amit Schendel
Senior Security Researcher

Jan 5, 2026·5 min read·10 visits

Executive Summary (TL;DR)

The Redaxo Backup Addon blindly trusted user input defining which directories to zip. Authenticated attackers can use directory traversal (`../`) in the `EXPDIR` parameter to force the server to archive and download sensitive files like `config.yml` (containing DB passwords) instead of the intended backup folders.

A critical Path Traversal vulnerability in the Redaxo CMS Backup Addon allows authenticated users to manipulate export parameters, enabling the extraction of sensitive system configuration files and database credentials.

Technical Appendix

CVSS Score
8.8/ 10
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS Probability
0.10%

Affected Systems

Redaxo CMS <= 5.20.1Redaxo Backup Addon <= 2.9.3

Affected Versions Detail

Product
Affected Versions
Fixed Version
Redaxo CMS
Redaxo
<= 5.20.15.20.2
Backup Addon
Redaxo
<= 2.9.32.9.4
AttributeDetail
CWECWE-22 (Improper Limitation of a Pathname to a Restricted Directory)
CVSS v3.18.8 (High)
Attack VectorNetwork
PrivilegesLow (Backup Permission)
ImpactConfidentiality, Integrity, Availability
Exploit StatusPoC Available
CWE-22
Path Traversal

The software uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the software does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

Vulnerability Timeline

Vulnerability discovered by Łukasz Rybak
2025-12-09
Official fix committed to repository
2026-01-05
Redaxo 5.20.2 released
2026-01-05
Advisory GHSA-824x-88xg-cwrv published
2026-01-05

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