# CVE-2026-117538: REDAXO before 5.21.0 Reflected XSS via Packages API function Parameter

Status: published. Published: 2026-10-27. Updated: 2026-11-04.

REDAXO before 5.21.0 contains a reflected cross-site scripting vulnerability in the backend packages API, where the function parameter is concatenated into an error message rendered without HTML escaping. Attackers can lure an authenticated backend user to a crafted link containing a valid CSRF token, executing JavaScript that performs same-origin actions or reads DOM data.

## Remediation

- fix: redaxo/source (Packagist): OSV reports a fixed version 5.21.0. Check the advisory for supported release branches. (source: OSV GHSA-xq4j-g85q-wf97) — https://github.com/advisories/GHSA-xq4j-g85q-wf97

## Affected products and versions

- redaxo / core: ≥ 0; < 5.21.0 (affected, semver); 5.21.0 (unaffected, semver). Source: CNA: VulnCheck
-  / redaxo/source (redaxo/source): 5.10.0 (affected, Packagist); 5.10.0-beta1 (affected, Packagist); 5.10.0-beta2 (affected, Packagist); 5.10.1 (affected, Packagist); 5.11.0 (affected, Packagist); 5.11.0-beta1 (affected, Packagist); 5.11.1 (affected, Packagist); 5.11.2 (affected, Packagist); 5.12.0 (affected, Packagist); 5.12.0-beta1 (affected, Packagist); 5.12.0-beta2 (affected, Packagist); 5.12.0-beta3 (affected, Packagist); 5.12.1 (affected, Packagist); 5.13.0 (affected, Packagist); 5.13.0-beta1 (affected, Packagist); 5.13.0-beta2 (affected, Packagist); 5.13.1 (affected, Packagist); 5.13.2 (affected, Packagist); 5.13.3 (affected, Packagist); 5.14.0 (affected, Packagist); 5.14.0-beta1 (affected, Packagist); 5.14.0-beta2 (affected, Packagist); 5.14.1 (affected, Packagist); 5.14.2 (affected, Packagist); 5.14.3 (affected, Packagist); 5.15.0 (affected, Packagist); 5.15.0-beta1 (affected, Packagist); 5.15.1 (affected, Packagist); 5.16.0 (affected, Packagist); 5.16.0-beta1 (affected, Packagist); 5.16.1 (affected, Packagist); 5.17.0 (affected, Packagist); 5.17.1 (affected, Packagist); 5.18.0 (affected, Packagist); 5.18.1 (affected, Packagist); 5.18.2 (affected, Packagist); 5.18.3 (affected, Packagist); 5.19.0 (affected, Packagist); 5.20.0 (affected, Packagist); 5.20.1 (affected, Packagist); 5.20.2 (affected, Packagist); 5.21.0-beta1 (affected, Packagist); Ecosystem version events: introduced 0; fixed 5.21.0. Source: OSV GHSA-xq4j-g85q-wf97

## Severity and prioritization

- CVSS 4.0: 2.1 (low); 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; source: CNA: VulnCheck

- CVSS 3.1: 4.1 (medium); CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:L; source: CNA: VulnCheck

- CVSS 4.0: 2.1 (low); 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/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; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 4.1 (medium); CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:L; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.18% as of 2026-11-04; percentile 7.51%

- SSVC: exploitation poc; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-79

## Exploit evidence

- exploit: https://github.com/redaxo/core/security/advisories/GHSA-xq4j-g85q-wf97 (ADP: CISA-ADP)

## References

- https://github.com/redaxo/core/security/advisories/GHSA-xq4j-g85q-wf97 (CNA: VulnCheck; vendor-advisory)

- https://www.vulncheck.com/advisories/redaxo-before-5.21.0-reflected-xss-via-packages-api-function-parameter (CNA: VulnCheck; third-party-advisory)

- https://github.com/redaxo/core/security/advisories/GHSA-xq4j-g85q-wf97 (ADP: CISA-ADP; exploit)

- https://github.com/redaxo/core/security/advisories/GHSA-xq4j-g85q-wf97 (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/redaxo-before-5.21.0-reflected-xss-via-packages-api-function-parameter (disclosure@vulncheck.com)

- https://github.com/redaxo/core/security/advisories/GHSA-xq4j-g85q-wf97 (134c704f-9b21-4f2e-91b3-4a467353bcc0)

- https://github.com/advisories/GHSA-xq4j-g85q-wf97 (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-xq4j-g85q-wf97 (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-117538; retrieved 2026-11-04; source updated 2026-11-04

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-117538; retrieved 2026-11-04; source updated 2026-11-04

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-xq4j-g85q-wf97; retrieved 2026-11-04; source updated 2026-10-28

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-117538; retrieved 2026-11-04; source updated Not reported

Revision: 68d4510aafba14f69f9f29eabaccfc078e1258cbc81920bd21d2a0c57a84de1f

Canonical: https://y2.dev/cve/CVE-2026-117538

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.