CVE-2026-48529CWE-284

GitHub MCP Server: Lockdown mode singleton in HTTP server causes cross-user GraphQL client confusion

Medium · published June 26, 2026

CVSS v3.1
6.0
EPSS
0%
Percentile
10.0
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
6.0 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L
CVSS v4.0
Not supplied
EPSS
0.00205 · 10.0th percentile
Weakness
CWE-284 · Improper Access Control
Published
2026-06-26T16:33Z
EPSS history
Timeline
  • 26 JUN 16:33Z
    GitHub MCP Server: Lockdown mode singleton in HTTP server causes cross-user GraphQL client confusion
    cvelistv5