# CVE-2026-117538: REDAXO reflected XSS in backend packages API

Source: https://junglewise.ai/threats/cve-2026-117538-redaxo-before-5-21-0-contains-a-reflected-cross-site-scripting  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-27. Updated: 2026-10-27  
License: CC BY 4.0 with a link back

CVE-2026-117538 · Severity: medium · CVSS 4.1 · Published 2026-10-27

REDAXO is a content management system used to build and manage websites. A reflected cross-site scripting vulnerability in the backend packages API allows attackers to trick authenticated administrators into visiting a malicious link, where injected JavaScript could read sensitive data from the admin interface or perform unauthorized actions on behalf of the victim.

Technologies: [REDAXO Core](https://junglewise.ai/threats/technologies/redaxo-core). Vendors: [REDAXO](https://junglewise.ai/threats/vendors/redaxo).

## Quick answers

**Is CVE-2026-117538 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-117538 being exploited in the wild.

**How severe is CVE-2026-117538?** Medium severity, with a CVSS score of 4.1, published 27 October 2026.

**Which products and versions are affected?** REDAXO Core before 5.21.0.

**Is there a fix for CVE-2026-117538?** Yes: fixed in 5.21.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-117538 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-117538?** Check whether you run REDAXO Core at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in 5.21.0

## Technical details

The function parameter in the backend packages API is concatenated directly into an exception message and rendered via rex_view::message() without HTML escaping, creating a reflected XSS. Exploitation requires a valid backend session, a valid CSRF token, and user interaction (clicking a malicious link). An attacker can execute arbitrary JavaScript in the victim's admin session to access DOM data or perform same-origin requests.

## Affected products

- REDAXO core before 5.21.0

## Timeline

- 2026-04-09: disclosed
- 2026-10-27: advisory

## References

- [https://github.com/redaxo/core/security/advisories/GHSA-xq4j-g85q-wf97](https://github.com/redaxo/core/security/advisories/GHSA-xq4j-g85q-wf97)
- [https://www.vulncheck.com/advisories/redaxo-before-5.21.0-reflected-xss-via-packages-api-function-parameter](https://www.vulncheck.com/advisories/redaxo-before-5.21.0-reflected-xss-via-packages-api-function-parameter)

## Related threats

- [REDAXO core authentication bypass in structure/history plugin](https://junglewise.ai/threats/cve-2026-117532-redaxo-core-from-5-3-0-before-5-21-4-contains-an-authentication)
- [REDAXO broken access control in slice operations](https://junglewise.ai/threats/cve-2026-116899-redaxo-before-5-21-4-contains-a-broken-access-control)
- [REDAXO missing authorization in structure/version and structure/history previews](https://junglewise.ai/threats/cve-2026-116897-redaxo-core-before-5-21-4-contains-a-missing-authorization)
- [REDAXO cross-site request forgery in safe mode toggle](https://junglewise.ai/threats/cve-2026-116895-redaxo-before-5-21-5-contains-a-cross-site-request-forgery)
- [REDAXO core missing authorization in package API](https://junglewise.ai/threats/cve-2026-116893-redaxo-core-before-5-21-5-contains-a-missing-authorization)