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OpenAdvisories
Medium · 6.0 CVE-2026-48529 EUVD-2026-39809GHSA-pjp5-fpmr-3349GO-2026-5779

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

Published Jun 26, 2026 · Updated Jun 27, 2026 · Assigned by GitHub_M

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.

Affected products

VendorProductAffectedFixed
github github-mcp-server >= 0.22.0, < 1.1.2 —

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
openSUSE Leap 16.0 govulncheck-vulndb 0.0.20260723T184607-160000.1.1 openSUSE-SU-2026:21483-1

Affected packages

EcosystemPackageAffectedFixedRecord
Go github.com/github/github-mcp-server >= 0.22.0, < 1.1.2 1.1.2 GHSA-pjp5-fpmr-3349

Advisories 1

References