CVE-2026-21857
Unknown Unknown - Not Provided
Path Traversal in REDAXO Backup Addon Allows Arbitrary File Access

Publication date: 2026-01-07

Last updated on: 2026-01-07

Assigner: GitHub, Inc.

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.
CVSS Scores
EPSS Scores
Probability:
Percentile:
Meta Information
Published
2026-01-07
Last Modified
2026-01-07
Generated
2026-06-16
AI Q&A
2026-01-08
EPSS Evaluated
2026-06-15
NVD
CVE-2026-21857
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
redaxo redaxo to 5.20.2 (exc)
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-24 The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize "../" sequences that can resolve to a location that is outside of that directory.
CWE-22 The product 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 product 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.
Attack-Flow Graph
AI Quick Actions
Instant insights powered by AI
Executive Summary

This vulnerability exists in the REDAXO content management system's Backup addon prior to version 5.20.2. Authenticated users with backup permissions can exploit a path traversal flaw in the file export functionality by manipulating the EXPDIR POST parameter. The addon does not properly validate this parameter against the allowed directories, allowing attackers to include arbitrary readable files from within the webroot in the backup archive by using relative paths like '../' or absolute paths inside the document root.

Impact Analysis

This vulnerability can allow an attacker with backup permissions to read arbitrary files within the webroot, potentially exposing sensitive information stored on the server. This could lead to unauthorized disclosure of confidential data, which may compromise the security and privacy of the system and its users.

Mitigation Strategies

Upgrade REDAXO to version 5.20.2 or later, as this version fixes the path traversal vulnerability in the Backup addon. Additionally, restrict backup permissions to trusted authenticated users only until the upgrade is applied.

Chat Assistant
Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-21857. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70
EPSS Chart