showdown - Cross-Site Scripting via Unescaped Metadata Title in completeHTMLDocument
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Passive
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- Cross-site scripting
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- Deferred Red Hat: fix deferred
Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-79.
Summary
showdown contains a cross-site scripting vulnerability in metadata title handling that allows attackers to inject arbitrary HTML and JavaScript. When completeHTMLDocument option is enabled, unescaped less-than and greater-than characters in markdown frontmatter metadata are inserted directly into HTML title tags, enabling attackers to break out of the title context and execute malicious scripts in the rendered page.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| showdown | showdown | up to 2.1.0 | — | No fix listed | CNA |
| — | showdown (npm) | up to 2.1.0 | — | No fix listed | GHSA-cr32-g25g-vxjj |
- showdown Vendorshowdown Affected up to 2.1.0 Fixed in — No fix listed CNA
- showdown (npm) Vendor— Affected up to 2.1.0 Fixed in — No fix listed GHSA-cr32-g25g-vxjj
Remediation
No fixed version listed by the sources yet.
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Multicluster Engine for Kubernetes | Affected | No fix yet: Fix deferred |
| Node HealthCheck Operator | Affected | No fix yet: Fix deferred |
| Red Hat 3scale API Management Platform 2 | Affected | No fix yet: Fix deferred |
| Red Hat Advanced Cluster Management for Kubernetes 2 | Affected | No fix yet: Fix deferred |
| Red Hat Ansible Automation Platform 2 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift AI (RHOAI) | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Virtualization 4 | Affected | No fix yet: Fix deferred |
| Red Hat Quay 3 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-59711
- 2026-10-03 Alias added: GHSA-cr32-g25g-vxjj
References
More showdown vulnerabilities
- TI-2026-42583 showdown - Stored XSS via Unescaped Table Header ID Attribute Injection CVSS 4.0MEDIUM 5.3
Sources
- CVE-2026-59711 · CVE Program
- CVE-2026-59711 · NVD
- FIRST EPSS
- GHSA-cr32-g25g-vxjj · GitHub Advisory Database · CC BY 4.0
- CVE-2026-59711 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences