# CVE-2026-65903: cure53 DOMPurify logic error in ADD_TAGS function bypasses FORBID_TAGS

Source: https://junglewise.ai/threats/cve-2026-65903-cure53-dompurify-logic-error-in-add-tags-function-bypasses-forbid  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-23. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-65903 · Severity: medium · CVSS 6.1 · Published 2026-07-23

DOMPurify is a widely-used HTML sanitizer library that removes potentially malicious content from user-supplied HTML. When configured with both the ADD_TAGS and FORBID_TAGS settings simultaneously, a logic flaw causes forbidden tags to be incorrectly allowed through due to short-circuit evaluation in the condition checking. An attacker who can inject HTML into a page using a vulnerable application could bypass tag restrictions and potentially inject malicious scripts or other harmful content.

Technologies: [dompurify (npm)](https://junglewise.ai/threats/technologies/dompurify). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-65903 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-65903 being exploited in the wild.

**How severe is CVE-2026-65903?** Medium severity, with a CVSS score of 6.1, published 23 July 2026.

**Which products and versions are affected?** dompurify (npm) <= 3.3.3, SEMVER:introduced=0,fixed=3.4.0.

**Is there a fix for CVE-2026-65903?** Yes. dompurify (npm): upgrade to 3.4.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-65903 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-65903?** Check whether you run dompurify (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- dompurify (npm): upgrade to 3.4.0 or later

  ```sh
  npm install dompurify@3.4.0
  ```


## Technical details

The vulnerability exists in src/purify.ts lines 1117–1123, where tag handling uses the condition: !(tagCheck(tagName)) && (!ALLOWED_TAGS[tagName] || FORBID_TAGS[tagName]). When tagCheck(tagName) returns true, the negation makes the entire left side false, short-circuiting the AND operator and preventing FORBID_TAGS[tagName] from being evaluated. This means tags added via the tagCheck function bypass the forbidden-tags list entirely. The root cause is a logic ordering issue: the code checks the user-defined tagCheck callback before consulting FORBID_TAGS, whereas on the attribute side (line 1214), FORBID_ATTR is checked first with an explicit continue statement. Attack preconditions require an application to configure DOMPurify with both ADD_TAGS as a function and FORBID_TAGS simultaneously. An attacker injecting HTML into such an application could craft tag payloads that pass the tagCheck function and bypass FORBID_TAGS restrictions. The fix is to reorder the check: evaluate FORBID_TAGS first and deny the tag before checking tagCheck. This issue was patched in version 3.4.0.

## Affected products

- Cure53 DOMPurify <= 3.3.3

## Identifiers

- CVE-2026-65903
- GHSA-39q2-94rc-95cp

## Timeline

- 2026-04-16: disclosed: Advisory GHSA-39q2-94rc-95cp published
- 2026-04-16: patched: Fixed in version 3.4.0

## References

- [https://github.com/cure53/DOMPurify/security/advisories/GHSA-39q2-94rc-95cp](https://github.com/cure53/DOMPurify/security/advisories/GHSA-39q2-94rc-95cp)
- [https://github.com/cure53/DOMPurify](https://github.com/cure53/DOMPurify)

## Related threats

- [DOMPurify SAFE_FOR_TEMPLATES bypass in shadow root content](https://junglewise.ai/threats/dompurify-safe-for-templates-bypass-split-template-expressions-survive-c23665cf)
- [DOMPurify IN_PLACE event handler bypass when hook removes parent or sibling](https://junglewise.ai/threats/dompurify-in-place-hook-that-removes-a-parent-or-sibling-leaves-the-3ea5d18f)
- [DOMPurify SMIL attributeName=href guard bypass in XHTML mode](https://junglewise.ai/threats/dompurify-smil-attributename-href-guard-is-skipped-when-parser-media-15a5efd2)
- [DOMPurify IN_PLACE mode XSS via rawtext element text content](https://junglewise.ai/threats/dompurify-in-place-returns-a-force-removed-rawtext-root-whose-text-16d9ac9e)
- [DOMPurify DOM XSS in IN_PLACE mode with afterSanitize hooks](https://junglewise.ai/threats/dompurify-in-place-node-removing-aftersanitize-hook-leaves-detached-3087e7fd)