Roslyn CodeLens MCP Server: Untrusted Roslyn Analyzer Execution via get_diagnostics Leads to Arbitrary Code Execution
Key facts
- Attack vector
- Local
- Privileges required
- None
- User interaction
- Required
- Attack complexity
- Low
- Impact type
- Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-94.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| MarcelRoozekrans | roslyn-codelens-mcp | 0.0.9 to before 1.17.0 | 1.17.0 | Patch available | CNA |
- roslyn-codelens-mcp VendorMarcelRoozekrans Affected 0.0.9 to before 1.17.0 Fixed in 1.17.0 Patch available CNA
Remediation
- Fix · CNA roslyn-codelens-mcp (MarcelRoozekrans) Fixed in 1.17.0
Timeline
- 2026-10-02 Threatist record created from CVE-2026-45555
References
Sources
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences