REDAXO has reflected XSS backend packages API via function parameter (CSRF token required)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

2.1 · CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-117538: 0.18% estimated exploitation activity in the next 30 days; percentile 7.50 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A reflected XSS vulnerability has been identified in the REDAXO backend. The `function` parameter is concatenated into an API error message and rendered without HTML escaping. ---

Details Root cause User input `function` is injected into an exception message, then rendered by `rex_view::error()` which delegates to `rex_view::message()` without HTML escaping. Vulnerable code (`redaxo/src/core/lib/packages/api_package.php`) : ```php $function = rex_request('function', 'string'); throw new rex_api_exception('Unknown package function "' . $function . '"!'); ``` Sink (`redaxo/src/core/lib/view.php`) : ```php return ' ' . $message . ' '; ``` Source -> sink flow * Source: `function` (GET) * Propagation: concatenated into the exception message * Sink: rendered via `rex_view::error()` -> `rex_view::message()` without escaping Authentication required: yes (backend session) ---

PoC - Exploit ```python #!/usr/bin/env python3 import re import…

Published by the source

10 Apr 2026, 19:40 UTC

Last modified by the source

28 Oct 2026, 02:56 UTC

Source last checked

28 Oct 2026, 06:30 UTC

1. Revision 2 · amended · 28 Oct 2026

   Amended from osv record GHSA-xq4j-g85q-wf97

2. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-xq4j-g85q-wf97

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# Patch Next advisory brief: CVE-2026-117538

Advisory: REDAXO has reflected XSS backend packages API via function parameter (CSRF token required)
IDs: CVE-2026-117538, GHSA-xq4j-g85q-wf97
Record: https://patchnext.com/advisories/ghsa-xq4j-g85q-wf97 (revision 2, source checked 28 Oct 2026, 06:30 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: redaxo/source 5.21.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist redaxo/source: affected < 5.21.0; fixed in 5.21.0

## Suggested inspection (read-only)
- Packagist redaxo/source: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on redaxo/source.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-xq4j-g85q-wf97 (OSV record GHSA-xq4j-g85q-wf97 lists affected ranges: Packagist redaxo/source >=0 <5.21.0 (fixed))
- Verified: https://github.com/advisories/GHSA-xq4j-g85q-wf97 (GitHub-reviewed advisory GHSA-xq4j-g85q-wf97 lists affected ranges: Packagist redaxo/source >=0 <5.21.0)

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