Advisories for Golang/Github.com/Github/Github-Mcp-Server package

A nil pointer dereference vulnerability in the GitHub MCP Server causes it to crash when receiving a malformed completion/complete request with missing or empty parameters. This allows any unauthenticated client to cause a complete denial of service.

When running in HTTP mode with –lockdown-mode enabled, the RepoAccessCache is implemented as a process-global singleton initialized with the first authenticated user's GraphQL client. All subsequent requests from different users share this singleton and their lockdown-related GraphQL queries are executed using the first user's credentials. The singleton is never updated to reflect later users' tokens.