GitHub MCP Server is GitHub's official MCP Server.
Date: 2026-06
Attack vector: auth-bypass
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2026-48529
CWE: CWE-284
CVSS: 6 (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L)

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.


Mitigations:

Architectural layers (MAESTRO):