DOMPurify: Prototype Pollution to XSS Bypass via CUSTOM_ELEMENT_HANDLING Fallback
Priority MEDIUM 64CWE-1321Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Required
- Attack complexity
- High
- Impact type
- Cross-site scripting
- Confidentiality · integrity · availability
- High · Low · None
- Fix status
- Partial Red Hat: 1 fixed, 30 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-79.
Summary
DOMPurify is a DOM-only cross-site scripting sanitizer for HTML, MathML, and SVG. Versions 3.0.1 through 3.3.3 are vulnerable to a prototype pollution-based XSS bypass. When an application uses `DOMPurify.sanitize()` with the default configuration (no `CUSTOM_ELEMENT_HANDLING` option), a prior prototype pollution gadget can inject permissive `tagNameCheck` and `attributeNameCheck` regex values into `Object.prototype`, causing DOMPurify to allow arbitrary custom elements with arbitrary attributes — including event handlers — through sanitization. Version 3.4.0 fixes the issue.
Why it matters now
Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.0027 19th percentileScored 2026-11-07
Fix Partial DOMPurify (cure53): 3.4.0dompurify (npm): 3.4.0Red Hat: 1 advisoryRed Hat: 1 fixed, 30 without a fix
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 |
|---|---|---|---|---|---|
| cure53 | DOMPurify | 3.0.1 to before 3.4.0 | 3.4.0 | Patch available | CNA |
| — | dompurify (npm) | 3.0.1 to before 3.4.0 | 3.4.0 | Patch available | GHSA-v9jr-rg53-9pgp |
- DOMPurify Vendorcure53 Affected 3.0.1 to before 3.4.0 Fixed in 3.4.0 Patch available CNA
- dompurify (npm) Vendor— Affected 3.0.1 to before 3.4.0 Fixed in 3.4.0 Patch available GHSA-v9jr-rg53-9pgp
Remediation
- Fix · CNA DOMPurify (cure53) Fixed in 3.4.0
- Fix · GHSA-v9jr-rg53-9pgp dompurify (npm) Fixed in 3.4.0 Advisory →
Red Hat 1 advisory
- RHSA-2026:86618 Released 2026-10-21 · Red Hat rating CriticalNew container image: rhceph-9.2
- Red Hat Ceph Storage 9.2 registry.redhat.io/rhceph/rhceph-9-rhel10
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Cryostat 4 | Affected | No fix yet: Fix deferred |
| Migration Toolkit for Virtualization | Affected | No fix yet: Fix deferred |
| Multicluster Engine for Kubernetes | Affected | No fix yet: Fix deferred |
| Node HealthCheck Operator | Affected | No fix yet: Fix deferred |
| OpenShift Lightspeed | Affected | No fix yet: Fix deferred |
| OpenShift Service Mesh 2 | Affected | No fix yet: Fix deferred |
| OpenShift Service Mesh 3 | Affected | No fix yet: Fix deferred |
| Red Hat 3scale API Management Platform 2 | Affected | No fix yet: Fix deferred |
| Red Hat Advanced Cluster Security 4 | Affected | No fix yet: Fix deferred |
| Red Hat Ansible Automation Platform 2 | Affected | No fix yet: Fix deferred |
| Red Hat Build of Podman Desktop | Affected | No fix yet: Fix deferred |
| Red Hat Ceph Storage 9 | Affected | No fix yet: Fix deferred |
| Red Hat Data Grid 8 | Affected | No fix yet: Fix deferred |
| Red Hat Developer Hub 1 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | 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 Dev Spaces | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift GitOps | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Virtualization 4 | Affected | No fix yet: Fix deferred |
| Red Hat Openshift Data Foundation 4 | Affected | No fix yet: Fix deferred |
| Red Hat Process Automation 7 | Affected | No fix yet: Fix deferred |
| Red Hat build of Apache Camel - HawtIO 4 | Affected | No fix yet: Fix deferred |
| Red Hat build of Apicurio Registry 2 | Affected | No fix yet: Fix deferred |
| Red Hat build of Apicurio Registry 3 | Affected | No fix yet: Fix deferred |
| Self-service automation portal 2 | Affected | No fix yet: Fix deferred |
| streams for Apache Kafka 2 | Affected | No fix yet: Fix deferred |
| streams for Apache Kafka 3 | Affected | No fix yet: Fix deferred |
| Red Hat Ceph Storage 9.2 | Fixed | RHSA-2026:86618 |
Not affected: 2 products
- Red Hat Ceph Storage 9.2
- Red Hat Hardened Images
Timeline
- 2026-10-02 Threatist record created from CVE-2026-41238
- 2026-10-03 Alias added: GHSA-v9jr-rg53-9pgp
- 2026-10-21 Fix available: RHSA-2026:86618 · Red Hat
- 2026-10-21 Fix available: Red Hat Ceph Storage 9.2 · Red Hat
- 2026-10-27 Affected versions changed · Red Hat
References
More cure53 vulnerabilities
- TI-2026-34986 DOMPurify XSS via `selectedcontent` re-clone CVSS 3.1HIGH 8.2
- TI-2025-30422 Path traversal in cure53 DOMPurify CVSS 3.1HIGH 7.5
- TI-2026-36811 DOMPurify IN_PLACE Sanitization Bypass via Attached Shadow Root Inside <template>.content CVSS 4.0MEDIUM 6.3
- TI-2026-36614 DOMPurify: IN_PLACE mode preserves attributes of a clobbered root element, allowing XSS via attacker-controlled root DOM CVSS 3.1MEDIUM 6.1
- TI-2026-36613 DOMPurify: Cross-realm IN_PLACE sanitization leaves executable markup intact via realm-bound `instanceof` checks CVSS 3.1MEDIUM 6.1
- TI-2026-29849 DOMPurify: FORBID_TAGS bypassed by function-based ADD_TAGS predicate (asymmetry with FORBID_ATTR fix) CVSS 4.0MEDIUM 6.0
Sources
- CVE-2026-41238 · CVE Program
- CVE-2026-41238 · NVD
- FIRST EPSS
- GHSA-v9jr-rg53-9pgp · GitHub Advisory Database · CC BY 4.0
- CVE-2026-41238 · 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