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CVE-2026-44990 critical CVSS 9.3

Cross-Site Scripting (XSS) in sanitize-html (CVE-2026-44990)

Summary

Cross-site scripting in sanitize-html (CVE-2026-44990). Confidential information can be exposed externally. Exploitable via xmp. Mitigation: upgrade to 2.17.4 or later.

Original description

The description as published by the source.

Summary

Under the default configuration, sanitize-html can turn attacker-controlled content inside a disallowed xmp element into live HTML or JavaScript. This is a sanitizer bypass in the default disallowedTagsMode: 'discard' path and can lead to stored XSS in applications that render sanitized output back to users.

Details

In sanitize-html@2.17.3, the default nonTextTags list includes only script, style, textarea, and option in index.js lines 138-142. That means disallowed xmp tags are not treated as "drop the entire contents" tags.

Later, in the ontext handler at index.js lines 569-577, the code special-cases textarea and xmp and appends their text content directly to the output without escaping:

} else if ((options.disallowedTagsMode === 'discard' || options.disallowedTagsMode === 'completelyDiscard') && (tag === 'textarea' || tag === 'xmp')) {
  result += text;
}

Because htmlparser2 treats xmp as a raw-text element, markup inside xmp is parsed as text on input but becomes live markup again once it is appended unescaped to the sanitized output.

This creates a default sanitizer bypass. For example, a disallowed wrapper can be used to smuggle or event-handler payloads through sanitization.

The README also appears to contradict the implementation. In the "Discarding the entire contents of a disallowed tag" section, the documented exception list names only style, script, textarea, and option, and does no…

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-2026-44990 has been found in sanitize-html.
Attackers can target a specific entry point like xmp over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 9.3/10.
What to do: upgrade sanitize-html to 2.17.4 or later.
If unsure, ask your IT team or search "sanitize-html CVE-2026-44990" on the vendor's site.

CVE-2026-44990 (sanitize-html) — CWE-79 / CVSS v3 9.3
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: xmp / nonTextTags / script / style
Patched: 2.17.4 — 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

Cross-site scripting (XSS) (CWE-79) exists in sanitize-html. Attackers reach the vulnerable code path via xmp without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of sanitize-html. Attack surface: xmp / nonTextTags / script / style.

🔥 Severity

Severity: Critical (CVSS 9.3/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 2.17.4.

🛡️ 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 'sanitize-html' . 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 'sanitize-html' . | 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 sanitize-html 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 sanitize-html to 2.17.4

    ステージング環境で 2.17.4 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 sanitize-html
[{"type":"SEMVER","events":[{"introduced":"2.17.3"},{"fixed":"2.17.4"}]}]

References

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