Vulnerability in dompurify (CVE-2026-65903)
Summary
Vulnerability in dompurify (CVE-2026-65903). Risk of unauthorized operations or information disclosure. Exploitable via ADD_TAGS. Mitigation: upgrade to 3.4.0 or later.
Original description
The description as published by the source.
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)
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-65903 has been found in dompurify.
Attackers can target a specific entry point like ADD_TAGS over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 6.1/10.
What to do: upgrade dompurify to 3.4.0 or later.
If unsure, ask your IT team or search "dompurify CVE-2026-65903" on the vendor's site.
CVE-2026-65903 (dompurify) — CWE-697 / CVSS v3 6.1
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: ADD_TAGS / EXTRA_ELEMENT_HANDLING.tagCheck / FORBID_TAGS / true
Patched: 3.4.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-697) exists in dompurify. Attackers reach the vulnerable code path via ADD_TAGS without authentication.
Check the vendor advisory for the affected versions of dompurify. Attack surface: ADD_TAGS / EXTRA_ELEMENT_HANDLING.tagCheck / FORBID_TAGS / true.
Severity: Medium (CVSS 6.1/10). Risk of unauthorized operations or information disclosure.
Update to 3.4.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'dompurify' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'dompurify' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
dompurifyを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade dompurify to 3.4.0ステージング環境で 3.4.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Ubuntu UBUNTU-CVE-2026-65903 node-dompurify
References
- advisory disclosure@vulncheck.com
- exploit disclosure@vulncheck.com
- web github.com