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

{
  "id": "7ad95cd0e1c07878d2e637d7bdcc4d39f43dce601dc439b57a5701677838282b",
  "url": "https://osv.dev/vulnerability/CVE-2026-48529",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "GitHub MCP Server: Lockdown mode singleton in HTTP server causes cross-user GraphQL client confusion",
    "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.",
    "evidence": "osv:CVE-2026-48529",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-48529",
      "aliases": [
        "CVE-2026-48529",
        "GHSA-pjp5-fpmr-3349",
        "GO-2026-5779"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/github/github-mcp-server",
              "type": "GIT",
              "events": [
                {
                  "introduced": "6a57e75d729f9767827bc4f96e80ff9bd8538a46"
                },
                {
                  "fixed": "b5397f6e3305531a1c534b90b2d347a70fa84da9"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0.22.0"
                      },
                      {
                        "fixed": "1.1.2"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.1.2"
                      }
                    ],
                    "source": "DESCRIPTION"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v1.1.1",
            "v1.1.0",
            "v1.0.5",
            "v1.0.4",
            "v1.0.3",
            "v1.0.2",
            "v1.0.1",
            "v1.0.0",
            "v0.33.1",
            "v0.33.0",
            "v0.32.0",
            "v0.31.0",
            "v0.30.3",
            "v0.30.2",
            "v0.30.1",
            "v0.30.0",
            "v0.29.0",
            "v0.28.1",
            "v0.28.0",
            "v0.27.0",
            "v0.26.3",
            "v0.26.2",
            "v0.26.1",
            "v0.26.0",
            "v0.25.0",
            "v0.24.1",
            "v0.24.0",
            "v0.22.0",
            "v0.23.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-48529.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:39.543842617Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48529.json",
        "https://github.com/github/github-mcp-server/security/advisories/GHSA-pjp5-fpmr-3349",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-48529"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-284"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48529.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-48529",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 507225,
  "published_at": "2026-06-26T16:33:32.688+00:00"
}