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CVE-2025-66416
Vulnerability in mcp (CVE-2025-66416)
Summary
vulnerability in mcp (CVE-2025-66416). Risk of unauthorized operations or information disclosure. Exploitable via ``FastMCP``. Mitigation: upgrade to `1.23.0` or later.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **CVE-2025-66416** has been found in mcp.
Attackers can target a specific entry point like ``FastMCP`` over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: ?/10.
What to do: upgrade mcp to **1.23.0** or later.
If unsure, ask your IT team or search "mcp CVE-2025-66416" on the vendor's site.
CVE-2025-66416 (mcp) — CWE-350 /
Attack surface: `FastMCP` / `TransportSecuritySettings` / `host` / `localhost`
Patched: `1.23.0` — 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.
❓ What is the problem
**A vulnerability** (CWE-350) exists in mcp. Attackers reach the vulnerable code path via ``FastMCP`` without authentication.
📍 Affected scope
mcp — . Attack surface: `FastMCP` / `TransportSecuritySettings` / `host` / `localhost`.
🔥 Severity
Severity: ?. Risk of unauthorized operations or information disclosure
🔧 How to fix
Update to **1.23.0**.
🛡️ 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 'mcp' .` 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 'mcp' . | 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 `mcp` 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 mcp to 1.23.0ステージング環境で 1.23.0 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
pip
mcp
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.23.0"}]}]
PyPI
mcp
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.23.0"}]}]
References
- advisory https://nvd.nist.gov/vuln/detail/CVE-2025-66416
- advisory https://github.com/advisories/GHSA-9h52-p55h-vw2f
- package https://github.com/modelcontextprotocol/python-sdk
- package https://pypi.org/project/mcp
- web https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-9h52-p55h-vw2f
- web https://github.com/modelcontextprotocol/python-sdk/commit/d3a184119e4479ea6a63590bc41f01dc06e3fa99
- web https://github.com/pypa/advisory-database/tree/main/vulns/mcp/PYSEC-2026-1617.yaml