CVE-2026-48529 json
GitHub MCP Server: Lockdown mode singleton in HTTP server causes cross-user GraphQL client confusion
published 4mo ago modified 17d ago also EUVD-2026-39809 , GHSA-pjp5-fpmr-3349 , GO-2026-5779
- cvss
- 6.0
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 5%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- go github.com/github/github-mcp-server 1.1.2
- github mcp_server 1.1.2
- govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
opensuse advisories openSUSE-SU-2026:21483-1
Is CVE-2026-48529 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- no
- Technical impact
- partial
- Assessed
- 4mo ago
Exploit prediction
0.17% chance of exploitation in the next 30 days, higher than 5% of all scored CVEs (FIRST EPSS, 2026-11-11).
Exploits and checks
- github.com https://github.com/github/github-mcp-server/security/advisories/GHSA-pjp5-fpmr-3349 referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 6.0 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L |
| GitHub | 3.1 | 6.0 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/github/github-mcp-server | >=0.22.0, <1.1.2 |
1.1.2 |
Affected products
- github github-mcp-server
Classification
- Weakness
-
- CWE-284 Improper Access Control
References
-
github.com
/github/github-mcp-server/security/advisories/GHSA-pjp5-fpmr-3349
exploit, web, advisory
-
github.com
/github/github-mcp-server
package
Sources
- CVE List CVE-2026-48529
- GitHub Advisory GHSA-pjp5-fpmr-3349
- NVD CVE-2026-48529
- OSV GO-2026-5779
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.