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CVE-2026-41159
Code Injection in mermaid (CVE-2026-41159)
Summary
code injection in mermaid (CVE-2026-41159). Risk of unauthorized operations or information disclosure. Exploitable via ``fontFamily``. Mitigation: upgrade to `10.9.6` or later.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **CVE-2026-41159** has been found in mermaid.
Attackers can target a specific entry point like ``fontFamily`` over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: ?/10.
What to do: upgrade mermaid to **10.9.6** or later.
If unsure, ask your IT team or search "mermaid CVE-2026-41159" on the vendor's site.
CVE-2026-41159 (mermaid) — CWE-94 /
Attack surface: `fontFamily` / `themeCSS` / `altFontFamily` / `secure`
Patched: `10.9.6` — 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
**arbitrary code execution** (CWE-94) exists in mermaid. Attackers reach the vulnerable code path via ``fontFamily`` without authentication.
📍 Affected scope
mermaid — . Attack surface: `fontFamily` / `themeCSS` / `altFontFamily` / `secure`.
🔥 Severity
Severity: ?. Risk of unauthorized operations or information disclosure
🔧 How to fix
Update to **10.9.6**.
🛡️ 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 'mermaid' .` against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response Actions (7 steps)
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'mermaid' . | 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 `mermaid` を grep し、稼働しているサービス・バージョンを把握する。
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6Apply patch patch
Upgrade mermaid to 10.9.6ステージング環境で 10.9.6 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と、Step 3 で見つけた異常検知の続報チェックを含めること。
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7Post-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 Step 3 と同じログクエリでアラート再発が無いか継続監視。
Affected packages
npm
mermaid
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"10.9.6"}]}]
References
- package https://github.com/mermaid-js/mermaid
- web https://github.com/mermaid-js/mermaid/security/advisories/GHSA-87f9-hvmw-gh4p
- web https://github.com/mermaid-js/mermaid/commit/64769738d5b59211e1decb471ffbaca8afec51aa
- web https://github.com/mermaid-js/mermaid/commit/a9d9f0d8eb790349121508688cd338253fd80d76
- web https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.15.0
- web https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6
- web https://github.com/advisories/GHSA-87f9-hvmw-gh4p