Vulnerability in GitHub Github-Mcp-Server

CVE-2026-48529

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.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 6.0 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L.

EPSS exploit prediction

EPSS: 0.002 (9.4th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 9th percentile — 9.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-48529: held from 0.002 to 0.002.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-48529?
CVE-2026-48529 is a medium-severity vulnerability in GitHub Github-Mcp-Server, classified under Improper Access Control. CVSS score: 6.0/10. Published 2026-06-26.
How severe is CVE-2026-48529?
Medium severity. CVSS v3 base score is 6.0 out of 10.