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

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Summary

CVECVE-2026-48529
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-26 17:16:33 UTC
Updated2026-06-26 17:16:33 UTC
DescriptionGitHub 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.

Risk And Classification

Primary CVSS: v3.1 6 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L

Problem Types: CWE-284 | CWE-284 CWE-284: Improper Access Control

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6MEDIUMCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L
3.1CNADECLARED6MEDIUMCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
Low

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Github Github-mcp-server affected >= 0.22.0, < 1.1.2 Not specified

References

ReferenceSourceLinkTags
github.com/github/github-mcp-server/security/advisories/GHSA-pjp5-fpmr-3349 [email protected] github.com
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