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CVE-2026-49458 medium CVSS 6.1

Vulnerability in dompurify (CVE-2026-49458)

Summary

Vulnerability in dompurify (CVE-2026-49458). Risk of unauthorized operations or information disclosure. Exploitable via instanceof. Mitigation: upgrade to 3.4.6 or later.

Original description

The description as published by the source.

Cross-realm IN_PLACE sanitization leaves executable markup intact via realm-bound instanceof checks

CWE: CWE-79 (XSS — Improper Neutralization of Input During Web Page Generation) via CWE-693 (Protection Mechanism Failure — realm-bound instanceof checks fail-open on foreign-realm DOM nodes) and CWE-501 (Trust Boundary Violation — foreign-realm nodes accepted for sanitization but later checks are bound to the parent realm)

Summary

DOMPurify.sanitize(node, { IN_PLACE: true }) accepts a DOM node from any same-origin realm (e.g. a node owned by an application-created iframe document), but several follow-on security checks compare the node against constructors from the parent realm. Because constructors are per-realm, instanceof HTMLFormElement, instanceof NamedNodeMap, instanceof DocumentFragment, and instanceof Element all return false for nodes belonging to the iframe's realm. The library therefore proceeds as if the foreign-realm form is not clobberable, the foreign-realm ``'s .content is not a document fragment, and the foreign-realm attached shadow root is not a document fragment — silently skipping the clobber/template-content/shadow-DOM sanitization branches that those checks gate. Attacker-controlled markup survives in form attributes, template content, and attached shadow roots, and executes when the application later inserts or activates the sanitized node.

Affected

  • DOMPurify ≤ 3.4.5, including main at `89da34e03ec17868e561f87f3747…

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-2026-49458 has been found in dompurify.
Attackers can target a specific entry point like instanceof 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 3.4.6 or later.
If unsure, ask your IT team or search "dompurify CVE-2026-49458" on the vendor's site.

CVE-2026-49458 (dompurify) — CWE-501 / CVSS v3 6.1
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: instanceof / false / main / _initDocument
Patched: 3.4.6 — 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-501) exists in dompurify. Attackers reach the vulnerable code path via instanceof without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of dompurify. Attack surface: instanceof / false / main / _initDocument.

🔥 Severity

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

🔧 How to fix

Update to 3.4.6.

🛡️ 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 3.4.6

    ステージング環境で 3.4.6 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":"SEMVER","events":[{"introduced":"0"},{"fixed":"3.4.6"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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