Is CVE-2026-21857 in the CISA KEV catalog?

No. CVE-2026-21857 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-21857?

CVE-2026-21857 has a CVSS v3 base score of 6.5 (MEDIUM).

What is the EPSS score for CVE-2026-21857?

CVE-2026-21857 has an EPSS score of 0.49% (39th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-21857?

Upgrade redaxo to 5.20.2 or later.

CVE & CISA-KEV Catalog

CVE-2026-21857

MEDIUM

6.5

CVSS v3

NVD

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.

CWE-22Path Traversal CWE-24

How to fix

Remediation Available

redaxoNVD

Affected:< 5.20.2Fixed in:5.20.2CVE-2026-21857derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredHigh

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N

Exploit Intelligence

0.49%probability of exploitation in 30 days

39thpercentile

Low risk: more likely to be exploited than 39% of all known CVEs.

References

Exploit1

github.com

Release Notes1

github.com

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-01-20.