CVE-2026-45555 Roslyn CodeLens MCP Server: Untrusted Roslyn Analyzer Execution via get_diagnostics Leads to Arbitrary Code Execution
An attacker can achieve arbitrary code execution by tricking a victim into opening a malicious project with the Roslyn CodeLens MCP Server.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-45555?
CVE-2026-45555 is a high-severity code injection vulnerability in MarcelRoozekrans roslyn-codelens-mcp, published on 29 May 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-94
Which versions are affected by CVE-2026-45555?
How do I fix CVE-2026-45555?
No fix has been published for CVE-2026-45555 yet. Limit exposure of the affected software until one is available.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-45555 being exploited?
There is no known exploitation of CVE-2026-45555 in the wild and no public exploit code.
Sources
Also known as GHSA-552p-8f74-6x7q.