CVE-2026-49978: Dompurify DOMPurify IN_PLACE Sanitization Bypass Vulnerability

MODERATE
Advisory Identifier: GHSA-rp9w-3fw7-7cwq
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CWE-79
Published
Advisory Summary

CVE-2026-49978 is a MODERATE dompurify in_place sanitization bypass vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Dompurify libraries in the npm ecosystem. The issue involves dompurify in_place sanitization bypass via attached shadow root inside <template>.content. Remediation is available by upgrading affected packages to version 3.4.7.

CVE-2026-49978 at a Glance

CVE Identifier CVE-2026-49978
GHSA Identifier GHSA-rp9w-3fw7-7cwq
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Dompurify
Package Ecosystem npm
Published Date
Last Updated

How to Fix CVE-2026-49978

To remediate this vulnerability, upgrade all affected Dompurify dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

dompurify fixed: 3.4.7 
npm install dompurify@3.4.7
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls dompurify

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-49978, inspect your project dependencies using npm:

npm ls dompurify

Analyze the terminal output to locate any version of Dompurify in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.4.7), your application is affected.

Note: The npm ls dompurify command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In Dompurify, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

If the HTML you give it contains a <template> element, and inside that template there's an element with a shadow DOM attached to it, DOMPurify quietly skips over the shadow contents. Whatever the attacker put in there - an image with an onerror handler, a link with a javascript: URL, even a full script - survives untouched. The moment the application uses that template the way templates are meant to be used (cloning it and inserting the result into the page), the malicious payload comes along and runs as if it had never been sanitized. From there an attacker gets everything XSS normally gets them: session cookies, stored tokens, the ability to act as the user, and the ability to leave persistent payloads behind for the next person who visits. [advisory.pdf](https://github.com/user-attachments/files/28275600/advisory.pdf) [poc.html](https://github.com/user-attachments/files/28275708/poc.html)

CVE-2026-49978 Affected Dompurify Versions

1 component(s)
Fixed Versions:
3.4.7
Product / Package Ecosystem Affected Versions Fixed Version
dompurify
npm/dompurify
npm
< 3.4.7
3.4.7

References

GitHub Advisory / Wiki ADVISORY
https://github.com/cure53/DOMPurify/security/advisories/GHSA-rp9w-3fw7-7cwq
Dompurify Source Repository REPOSITORY
https://github.com/cure53/DOMPurify

Frequently Asked Questions

What is CVE-2026-49978?
CVE-2026-49978 is a security vulnerability in Dompurify involving DOMPurify IN_PLACE Sanitization Bypass via Attached Shadow Root Inside <template>.content under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Dompurify versions are affected?
Affected versions include releases prior to 3.4.7 across affected packages: dompurify.
What version fixes CVE-2026-49978?
Upgrading to 3.4.7 (or the latest patched release for your respective branch) resolves the vulnerability.
Is dompurify affected?
Yes, dompurify is affected in releases prior to 3.4.7. Upgrade your dependency to 3.4.7 or later.
What CWE is associated with CVE-2026-49978?
CVE-2026-49978 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check npm dependencies for CVE-2026-49978?
Run the dependency tree command: 'npm ls dompurify'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-rp9w-3fw7-7cwq",
  "modified" : "2026-06-15T20:01:45Z",
  "published" : "2026-06-15T20:01:45Z",
  "aliases" : [ "CVE-2026-49978" ],
  "summary" : "DOMPurify IN_PLACE Sanitization Bypass via Attached Shadow Root Inside <template>.content",
  "details" : "If the HTML you give it contains a <template> element, and inside that template there's an element with a shadow DOM attached to it, DOMPurify quietly skips over the shadow contents. Whatever the attacker put in there - an image with an onerror handler, a link with a javascript: URL, even a full script - survives untouched. The moment the application uses that template the way templates are meant to be used (cloning it and inserting the result into the page), the malicious payload comes along and runs as if it had never been sanitized. From there an attacker gets everything XSS normally gets them: session cookies, stored tokens, the ability to act as the user, and the ability to leave persistent payloads behind for the next person who visits.\n\n[advisory.pdf](https://github.com/user-attachments/files/28275600/advisory.pdf)\n\n[poc.html](https://github.com/user-attachments/files/28275708/poc.html)",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "dompurify"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.4.7"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 3.4.6"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/cure53/DOMPurify/security/advisories/GHSA-rp9w-3fw7-7cwq"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/cure53/DOMPurify"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-15T20:01:45Z",
    "nvd_published_at" : null
  }
}