{"id":"CVE-2025-62801","aliases":["GHSA-rj5c-58rq-j5g5","PYSEC-2026-1365"],"url":"https://o3.security/vulnerability/CVE-2025-62801","summary":"FastMCP vulnerable to windows command injection in FastMCP Cursor installer via server_name","details":"### Summary\nA command-injection vulnerability lets any attacker who can influence the server_name field of an MCP execute arbitrary OS commands on Windows hosts that run fastmcp install cursor\n\n### Details\n1. generate_cursor_deeplink(server_name, …) embeds server_name verbatim in a cursor://…?name= query string.\n2. open_deeplink() is invoked with shell=True only on Windows. That calls cmd.exe /c start <deeplink>.\n3. Any cmd metacharacter inside server_name (&, |, >, ^, …) escapes the start command and spawns an attacker-chosen process.\n\n### PoC\nserver.py \n```\n\nimport random\nfrom fastmcp import FastMCP\n\nmcp = FastMCP(name=\"test&calc\")\n\n@mcp.tool\ndef roll_dice(n_dice: int) -> list[int]:\n    \"\"\"Roll `n_dice` 6-sided dice and return the results.\"\"\"\n    return [random.randint(1, 6) for _ in range(n_dice)]\n\nif __name__ == \"__main__\":\n    mcp.run()\n```\n\nthen run in the terminal:\n`fastmcp install cursor server.py`\n\n### Impact\nOS Command / Shell Injection (CWE-78)\nEvery Windows host that runs fastmcp install cursor is at risk. Developers on their local workstations, CI/CD agents and corporate build machines alike.","published":"2025-10-28T21:36:41.167Z","modified":"2026-10-28T02:30:49.784656178Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"fastmcp","fixedVersion":"2.13.0"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/62xxx/CVE-2025-62801.json"},{"type":"ADVISORY","url":"https://github.com/jlowin/fastmcp/security/advisories/GHSA-rj5c-58rq-j5g5"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-62801"},{"type":"PACKAGE","url":"https://github.com/jlowin/fastmcp"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-28T02:30:49.784656178Z"}}