GHSA-39q2-94rc-95cp

Suggest an improvement
Source
https://github.com/advisories/GHSA-39q2-94rc-95cp
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-39q2-94rc-95cp/GHSA-39q2-94rc-95cp.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-39q2-94rc-95cp
Downstream
Related
Published
2026-04-16T00:46:35Z
Modified
2026-04-16T23:29:14.344521774Z
Severity
  • 5.3 (Medium) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N CVSS Calculator
Summary
DOMPurify's ADD_TAGS function form bypasses FORBID_TAGS due to short-circuit evaluation
Details

Summary

In src/purify.ts:1117-1123, ADD_TAGS as a function (via EXTRA_ELEMENT_HANDLING.tagCheck) bypasses FORBID_TAGS due to short-circuit evaluation.

The condition:

!(tagCheck(tagName)) && (!ALLOWED_TAGS[tagName] || FORBID_TAGS[tagName])

When tagCheck(tagName) returns true, the entire condition is false and the element is kept — FORBID_TAGS[tagName] is never evaluated.

Inconsistency

This contradicts the attribute-side pattern at line 1214 where FORBID_ATTR explicitly wins first:

if (FORBID_ATTR[lcName]) { continue; }

For tags, FORBID should also take precedence over ADD.

Impact

Applications using both ADD_TAGS as a function and FORBID_TAGS simultaneously get unexpected behavior — forbidden tags are allowed through. Config-dependent but a genuine logic inconsistency.

Suggested Fix

Check FORBID_TAGS before tagCheck:

if (FORBID_TAGS[tagName]) { /* remove */ }
else if (tagCheck(tagName) || ALLOWED_TAGS[tagName]) { /* keep */ }

Affected Version

v3.3.3 (commit 883ac15)

Database specific 
{
    "severity": "MODERATE",
    "github_reviewed": true,
    "nvd_published_at": null,
    "github_reviewed_at": "2026-04-16T00:46:35Z",
    "cwe_ids": [
        "CWE-783"
    ]
}
References

Affected packages

npm / dompurify

Package

Name
dompurify
View open source insights on deps.dev
Purl
pkg:npm/dompurify

Affected ranges

Type
SEMVER
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
3.4.0

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-39q2-94rc-95cp/GHSA-39q2-94rc-95cp.json"
last_known_affected_version_range 
"<= 3.3.3"