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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-48529: 0.17% estimated exploitation activity in the next 30 days; percentile 5.84 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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. Details The singleton is defined in pkg/lockdown/lockdown.go: In HTTP mode, pkg/github/dependencies.go calls this per request: The singleton's internal client field is never updated after the first initialization. All lockdown GraphQL queries that check repository access and visibility (queryRepoAccessInfo, called by IsSafeContent) run under the first authenticated user's token for the lifetime of the process. IsSafeContent is called in at least six places across pkg/github/issues.go and pkg/github/pullrequests.go to decide whether to trust or sanitize content from external…

Published by the source

25 Jun 2026, 21:32 UTC

Last modified by the source

25 Jun 2026, 21:32 UTC

Source last checked

26 Oct 2026, 15:24 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-pjp5-fpmr-3349

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# Patch Next advisory brief: CVE-2026-48529

Advisory: GitHub MCP Server: Lockdown mode singleton in HTTP server causes cross-user GraphQL client confusion
IDs: CVE-2026-48529, GHSA-pjp5-fpmr-3349
Record: https://patchnext.com/advisories/cve-2026-48529 (revision 1, source checked 26 Oct 2026, 15:24 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/github/github-mcp-server 1.1.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/github/github-mcp-server: affected >= 0.22.0, < 1.1.2; fixed in 1.1.2

## Suggested inspection (read-only)
- Go github.com/github/github-mcp-server: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/github/github-mcp-server.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-pjp5-fpmr-3349 (GitHub-reviewed advisory GHSA-pjp5-fpmr-3349 lists affected ranges: Go github.com/github/github-mcp-server >=0.22.0 <1.1.2)

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