CVE-2026-48529
GitHub MCP Server: Lockdown mode singleton in HTTP server causes cross-user GraphQL client confusion
- State
- Published
- Severity
- 6.0 Medium
- Published
- Jun 26, 2026
- Updated
- Jun 27, 2026
- Reserved
- May 21, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 6.0 Medium | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L | GitHub_M |
Weaknesses
- CWE-284 Improper Access Control
Affected Products
| Product | Versions |
|---|---|
github-mcp-servergithub |
|
References
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