CVE-2026-21857 - Redaxo Plugin
CVE-2026-21857
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.
CVE-2026-21857
HIGH
CVSS 8.3
Published 2026-01-07
Updated 2026-01-20
AI Risk Critical (94/100)
Active Exploit: Likely
Published Exploit: Public exploit references found
Priority: P1 Immediate
Severity Band
HIGH
CVSS Vector
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Affected Components
1
Reference Links
2
AI Risk Engine
Critical (94/100)
Exploitability
High
Active Exploitation
Likely
Published Exploit Status
Public exploit references found
AI Context
Machine-generated threat intelligence
AI
Updated 12 days ago
AI enriched 12 days ago (2026-04-09 08:08 UTC)
Technical Summary
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…
Potential Impact
Severity is HIGH (CVSS 8.3). Depending on deployment context, affected components may be exposed to unauthorized actions or data integrity risk.
Exploitability Assessment
Exploitability is assessed as High based on published exploit references.
Primary risk drivers: published exploit references
Mitigation Recommendations
Validate affected product versions, prioritize patching, and monitor references for vendor remediation guidance. If immediate patching is not possible, apply compensating controls and limit exposure of vulnerable surfaces.
Detection & Monitoring
Track authentication anomalies, unexpected file writes, and suspicious plugin API activity around affected components.
Business Impact Lens
Prioritize remediation where affected components process customer data, admin sessions, or Internet-exposed workflows.