Code Injection in csharp (CVE-2026-45555, CVSS 7.8)

Summary

code injection in csharp (CVE-2026-45555). Successful exploitation can lead to full system takeover. Exploitable via get_diagnostics. Mitigation: upgrade to 1.17.0 or later.

Original description

The description as published by the source.

Roslyn CodeLens MCP Server is a Roslyn-based MCP server providing semantic code intelligence for .NET codebases. From 0.0.9 to 1.17.0, the get_diagnostics MCP tool loads and executes all DiagnosticAnalyzer assemblies referenced by the target solution without any allowlist, signature check, or user confirmation; includeAnalyzers defaults to true, so no explicit opt-in is required. An attacker who can place a malicious .csproj referencing an attacker-controlled DLL in a location the victim opens with the MCP server will achieve arbitrary code execution in the server process with the server's OS privileges. This vulnerability is fixed in 1.17.0.

Source: NIST National Vulnerability Database NVD

AI summary

Written by an external AI model and may contain mistakes. Check the original description and references below before acting on it.

A vulnerability tracked as CVE-2026-45555 has been found in csharp.
Attackers can target a specific entry point like get_diagnostics over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 7.8/10.
What to do: upgrade csharp to 1.17.0 or later.
If unsure, ask your IT team or search "csharp CVE-2026-45555" on the vendor's site.

CVE-2026-45555 (csharp) — CWE-94 / CVSS v3 7.8
Attack vector: local / unauthenticated
Attack surface: get_diagnostics / DiagnosticAnalyzer / includeAnalyzers / true
Affected: >= 0.0.9, < 1.17.0
Patched: 1.17.0 — 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

get_diagnostics MCPツールが不正なDLLを実行可能な脆弱性

📍 Affected scope

Roslyn CodeLens MCP Server バージョン0.0.9から1.17.0

🔥 Severity

攻撃者が任意のコードをサーバに実行させることが可能

🔧 How to fix

バージョン1.17.0にアップデートする

🛡️ Workaround

影響を受けるバージョンを使用しない

🔍 Detection

不正なcsprojファイルを確認することで検出可能

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

1
Identify exposure identify
```
grep -r 'csharp' . | 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 csharp を grep し、稼働しているサービス・バージョンを把握する。
2
Match against affected range verify
```
Confirm if version satisfies `>= 0.0.9, < 1.17.0`
```
Step 1 で見つかったバージョンが影響範囲 >= 0.0.9, < 1.17.0 に該当するか照合。本番で稼働中ならインシデント扱い。
6
Apply patch patch
```
Upgrade csharp to 1.17.0
```
ステージング環境で 1.17.0 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。
7
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 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。

References

web github.com