medium6.0
CVE-2026-48529
GitHub MCP Server: Lockdown mode singleton in HTTP server causes cross-user GraphQL client confusion
Impact
GitHub MCP Server is GitHub's official MCP Server. From 0.22.0 until 1.1.2, 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. This vulnerability is fixed in 1.1.2.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| go | github.com/github/github-mcp-server | >= 0.22.0, < 1.1.2 | 1.1.2 |