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CVE-2026-42559
high
CVSS 8.8
Vulnerability in rmcp (CVE-2026-42559)
Summary
vulnerability in rmcp (CVE-2026-42559). Successful exploitation can lead to full system takeover. Exploitable via `Host header`. Mitigation: upgrade to `1.4.0` or later.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **CVE-2026-42559** has been found in rmcp.
Attackers can target a specific entry point like `Host header` over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 8.8/10.
What to do: upgrade rmcp to **1.4.0** or later.
If unsure, ask your IT team or search "rmcp CVE-2026-42559" on the vendor's site.
CVE-2026-42559 (rmcp) — CWE-346 / CVSS v3 8.8
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: Host header / `rmcp` / `Host` / `Origin`
Patched: `1.4.0` — 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-346) exists in rmcp. Attackers reach the vulnerable code path via `Host header` without authentication.
📍 Affected scope
rmcp — . Attack surface: Host header / `rmcp` / `Host` / `Origin`.
🔥 Severity
Severity: High (CVSS 8.8/10). Successful exploitation can lead to full system takeover
🔧 How to fix
Update to **1.4.0**.
🛡️ 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 'rmcp' .` 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
-
1Identify exposure identify
grep -r 'rmcp' . | 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 `rmcp` を grep し、稼働しているサービス・バージョンを把握する。
-
6Apply patch patch
Upgrade rmcp to 1.4.0ステージング環境で 1.4.0 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。
-
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
crates.io
rmcp
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.4.0"}]}]
crates.io
dynoxide-rs
[{"type":"SEMVER","events":[{"introduced":"0.9.3"},{"fixed":"0.9.13"}]}]
rust
rmcp
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.4.0"}]}]
npm
dynoxide
[{"type":"SEMVER","events":[{"introduced":"0.9.3"},{"fixed":"0.9.13"}]}]
References
- advisory https://nvd.nist.gov/vuln/detail/CVE-2026-42559
- package https://github.com/modelcontextprotocol/rust-sdk
- package https://crates.io/crates/dynoxide-rs
- package https://github.com/nubo-db/dynoxide
- web https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-89vp-x53w-74fx
- web https://github.com/modelcontextprotocol/rust-sdk/issues/815
- web https://github.com/modelcontextprotocol/rust-sdk/pull/764
- web https://modelcontextprotocol.io/specification/2025-06-18/basic/transports#security-warning
- web https://rustsec.org/advisories/RUSTSEC-2026-0140.html
- web https://github.com/nubo-db/dynoxide/security/advisories/GHSA-fvh2-gm75-j4j7
- web https://github.com/nubo-db/dynoxide/releases/tag/v0.9.13
- web https://github.com/modelcontextprotocol/rust-sdk/commit/8e22aa2de28df5a285eed87c11cd89bf15fa90d3
- web https://github.com/modelcontextprotocol/rust-sdk/issues/822
- web https://github.com/advisories/GHSA-89vp-x53w-74fx