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DompurifyApplication · Cure53

CVE-2026-49978

MEDIUM · 6.1 CVSS v3.1 Published 2026-07-14
Fix available
A fix is available. Upgrade to 3.4.7 or later.
See remediation →
68/100
Remediation priority · Elevated
Public exploit Remotely reachable No privileges Patch available 5 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
DOMPurify is a DOM-only cross-site scripting sanitizer for HTML, MathML, and SVG. Prior to 3.4.7, DOMPurify IN_PLACE sanitization could skip shadow contents attached to an element inside <template>.content, allowing attacker-controlled markup such as event handlers, JavaScript URLs, or scripts to survive and execute when an application cloned and inserted the sanitized template. This issue is fixed in version 3.4.7.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

DOMPurify's IN_PLACE sanitization fails to sanitize shadow DOM contents attached to elements within <template> elements. When applications later clone and insert these sanitized templates into the DOM, malicious markup (event handlers, javascript: URLs, scripts) that was skipped during sanitization can execute.

MitigationUpgrade DOMPurify to version 3.4.7 or later. Avoid using IN_PLACE sanitization on templates that will be cloned until the upgrade is applied.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
DompurifyApplication
Affected:< 3.4.7

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify DOMPurify version
    Check your package.json, package-lock.json, or the dompurify dist file for the version number. Look for 'dompurify' in dependencies and note the version string.
    Affected if The version is lower than 3.4.7 (e.g., 3.4.6, 3.4.5, 3.0.0, etc.)
  2. Find IN_PLACE usage in code
    Search your codebase for DOMPurify sanitization calls that include IN_PLACE: true or config settings with IN_PLACE enabled. Search patterns like 'IN_PLACE' or 'dompurify.sanitize' with in-place configuration.
    Affected if IN_PLACE mode is being used when sanitizing template content
  3. Check if templates contain shadow DOM
    Examine your template HTML/JSX to see if any <template> elements contain or will have shadow DOM attached (via attachShadow or shadowRoot). Look for patterns like template.content, template.innerHTML, or attachShadow calls on template elements.
    Affected if Templates being sanitized contain or will contain shadow DOM content
  4. Verify template cloning behavior
    Search your codebase for code that clones sanitized templates and inserts them into the document. Look for patterns like cloneNode(true), importNode, template.content.cloneNode, or appending template content to the live DOM.
    Affected if Sanitized templates are later cloned and inserted into the DOM after sanitization
  5. Confirm shadow DOM is not sanitized during clone
    If you can inspect runtime behavior, verify that shadow DOM content attached to cloned templates was not processed by DOMPurify's sanitization.
    Affected if Shadow DOM content within templates is not being sanitized before DOM insertion

You are affected if you use DOMPurify version below 3.4.7 with IN_PLACE mode enabled on templates that contain shadow DOM, and those templates are subsequently cloned and inserted into the live DOM.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 3.4.7 or later
Fixed in 3.4.7
Vendor patch github.com →
Interim mitigation

Upgrade DOMPurify to version 3.4.7 or later. Avoid using IN_PLACE sanitization on templates that will be cloned until the upgrade is applied.

Recommended fix High confidence

DOMPurify 3.4.7

  1. Upgrade DOMPurify to version 3.4.7 or later by running `npm install [email protected]` or `yarn add [email protected]`
  2. If using a package-lock.json or yarn.lock file, regenerate it to lock to the new version
  3. Verify the upgrade was successful by checking the installed version with `npm list dompurify`
  4. Test your sanitization implementation to confirm templates with shadow DOM content are properly sanitized
  5. If using a bundler, rebuild your application to bundle the updated DOMPurify library

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Dompurify Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing3.0 h
  • Review / QA2.0 h
8.0 hours of engineering $1,390
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,224.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-49978 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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