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CVE-2026-65899 medium CVSS 6.1

Vulnerability in dompurify (CVE-2026-65899)

Summary

Vulnerability in dompurify (CVE-2026-65899). Risk of unauthorized operations or information disclosure. Exploitable via TRUSTED_TYPES_POLICY. Mitigation: upgrade to 3.4.9 or later.

Original description

The description as published by the source.

Impact

A DOMPurify instance that is reused across trust boundaries can stay bound to a previously supplied TRUSTED_TYPES_POLICY even after clearConfig() is called. A later caller that requests RETURN_TRUSTED_TYPE receives a TrustedHTML object created by the old policy, not by a clean default configuration.

If the old policy is unsafe or controlled by a less-trusted integration, this turns a later "default" sanitize call into script execution at a Trusted Types sink. TRUSTED_TYPES_POLICY: null on the later call also does not clear the retained policy.
dompurify-trusted-types-policy-survives-clearconfig-poc.js

Affected version

Tested against DOMPurify 3.4.8, repository commit 825e617753ac1169306a542d3174a77f717a0cf6.

Root cause

_parseConfig() overwrites trustedTypesPolicy when cfg.TRUSTED_TYPES_POLICY is truthy, but the default/null path only initializes the internal policy when trustedTypesPolicy === undefined. Once a custom policy has been set, later default config parsing leaves it in place.

Relevant code:

  • src/purify.ts:786-812 accepts and stores cfg.TRUSTED_TYPES_POLICY.
  • src/purify.ts:813-832 does not reset an existing policy when config has no policy or has TRUSTED_TYPES_POLICY: null.
  • src/purify.ts:2123-2125 signs the final serialized HTML with the retained policy when RETURN_TRUSTED_TYPE is true.
  • `src/p…

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-2026-65899 has been found in dompurify.
Attackers can target a specific entry point like TRUSTED_TYPES_POLICY 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 3.4.9 or later.
If unsure, ask your IT team or search "dompurify CVE-2026-65899" on the vendor's site.

CVE-2026-65899 (dompurify) — CWE-693 / CVSS v3 6.1
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: TRUSTED_TYPES_POLICY / RETURN_TRUSTED_TYPE / TrustedHTML / trustedTypesPolicy
Patched: 3.4.9 — 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.

❓ What is the problem

A vulnerability (CWE-693) exists in dompurify. Attackers reach the vulnerable code path via TRUSTED_TYPES_POLICY without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of dompurify. Attack surface: TRUSTED_TYPES_POLICY / RETURN_TRUSTED_TYPE / TrustedHTML / trustedTypesPolicy.

🔥 Severity

Severity: Medium (CVSS 6.1/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 3.4.9.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

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

  1. 1
    Identify 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。

  2. 2
    Apply patch patch 
    Upgrade dompurify to 3.4.9

    ステージング環境で 3.4.9 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。

  3. 3
    Post-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

npm dompurify
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.4.9"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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