Vulnerability-Lookup

PYSEC-2026-2475

Vulnerability from pysec - Published: 2026-07-13 14:36 - Updated: 2026-07-13 16:04

Details

Server names containing shell metacharacters (e.g., &) can cause command injection on Windows when passed to fastmcp install claude-code or fastmcp install gemini-cli. These install paths use subprocess.run() with a list argument, but on Windows the target CLIs often resolve to .cmd wrappers that are executed through cmd.exe, which interprets metacharacters in the flattened command string.

PoC:

from fastmcp import FastMCP

mcp = FastMCP(name="test&calc")

@mcp.tool
def roll_dice(n_dice: int) -> list[int]:
    """Roll `n_dice` 6-sided dice and return the results."""
    return [random.randint(1, 6) for _ in range(n_dice)]

fastmcp install claude-code server.py   # or: fastmcp install gemini-cli server.py

On Windows, this opens Calculator via the &calc in the server name.

Impact: Arbitrary command execution with the privileges of the user running fastmcp install. Affects Windows hosts where the target CLI (one of claude, gemini) is installed as a .cmd wrapper. Does not affect macOS/Linux, and does not affect config-file-based install targets (cursor, goose, mcp-json).

Patched in #3522 by validating server names to reject shell metacharacters.

Severity

6.7 (Medium)


                  
                    CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H

Impacted products

Name	purl
fastmcp	pkg:pypi/fastmcp

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "fastmcp",
        "purl": "pkg:pypi/fastmcp"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.2.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.1.0",
        "0.2.0",
        "0.3.0",
        "0.3.1",
        "0.3.2",
        "0.3.3",
        "0.3.4",
        "0.3.5",
        "0.4.0",
        "0.4.1",
        "1.0",
        "2.0.0",
        "2.1.0",
        "2.1.1",
        "2.1.2",
        "2.10.0",
        "2.10.1",
        "2.10.2",
        "2.10.3",
        "2.10.4",
        "2.10.5",
        "2.10.6",
        "2.11.0",
        "2.11.1",
        "2.11.2",
        "2.11.3",
        "2.12.0",
        "2.12.0rc1",
        "2.12.1",
        "2.12.2",
        "2.12.3",
        "2.12.4",
        "2.12.5",
        "2.13.0",
        "2.13.0.1",
        "2.13.0.2",
        "2.13.0rc1",
        "2.13.0rc2",
        "2.13.0rc3",
        "2.13.1",
        "2.13.2",
        "2.13.3",
        "2.14.0",
        "2.14.1",
        "2.14.2",
        "2.14.3",
        "2.14.4",
        "2.14.5",
        "2.14.6",
        "2.14.7",
        "2.2.0",
        "2.2.1",
        "2.2.10",
        "2.2.2",
        "2.2.3",
        "2.2.4",
        "2.2.5",
        "2.2.6",
        "2.2.7",
        "2.2.8",
        "2.2.9",
        "2.3.0",
        "2.3.0rc1",
        "2.3.1",
        "2.3.2",
        "2.3.3",
        "2.3.4",
        "2.3.5",
        "2.4.0",
        "2.5.0",
        "2.5.1",
        "2.5.2",
        "2.6.0",
        "2.6.1",
        "2.7.0",
        "2.7.1",
        "2.8.0",
        "2.8.1",
        "2.9.0",
        "2.9.1",
        "2.9.2",
        "3.0.0",
        "3.0.0b1",
        "3.0.0b2",
        "3.0.0rc1",
        "3.0.0rc2",
        "3.0.0rc3",
        "3.0.1",
        "3.0.2",
        "3.1.0",
        "3.1.1"
      ]
    }
  ],
  "aliases": [
    "CVE-2025-64340",
    "GHSA-m8x7-r2rg-vh5g"
  ],
  "details": "Server names containing shell metacharacters (e.g., `\u0026`) can cause command injection on Windows when passed to `fastmcp install claude-code` or `fastmcp install gemini-cli`. These install paths use `subprocess.run()` with a list argument, but on Windows the target CLIs often resolve to `.cmd` wrappers that are executed through `cmd.exe`, which interprets metacharacters in the flattened command string.\n\nPoC:\n```python\nfrom fastmcp import FastMCP\n\nmcp = FastMCP(name=\"test\u0026calc\")\n\n@mcp.tool\ndef roll_dice(n_dice: int) -\u003e 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```\n\n```\nfastmcp install claude-code server.py   # or: fastmcp install gemini-cli server.py\n```\n\nOn Windows, this opens Calculator via the `\u0026calc` in the server name.\n\nImpact:\nArbitrary command execution with the privileges of the user running `fastmcp install`. Affects Windows hosts where the target CLI (one of claude, gemini) is installed as a `.cmd` wrapper. Does not affect macOS/Linux, and does not affect config-file-based install targets (cursor, goose, mcp-json).\n\nPatched in #3522 by validating server names to reject shell metacharacters.",
  "id": "PYSEC-2026-2475",
  "modified": "2026-07-13T16:04:02.290801Z",
  "published": "2026-07-13T14:36:46.084219Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-m8x7-r2rg-vh5g"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jlowin/fastmcp/security/advisories/GHSA-m8x7-r2rg-vh5g"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-64340"
    },
    {
      "type": "WEB",
      "url": "https://github.com/PrefectHQ/fastmcp/pull/3522"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/PrefectHQ/fastmcp"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/fastmcp"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-m8x7-r2rg-vh5g"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "FastMCP has a Command Injection vulnerability - Gemini CLI"
}

CVE-2025-64340 (GCVE-0-2025-64340)

Vulnerability from cvelistv5 – Published: 2026-04-03 15:16 – Updated: 2026-04-03 16:12

Title

FastMCP has a Command Injection vulnerability - Gemini CLI

Summary

FastMCP is the standard framework for building MCP applications. Prior to version 3.2.0, server names containing shell metacharacters (e.g., &) can cause command injection on Windows when passed to fastmcp install claude-code or fastmcp install gemini-cli. These install paths use subprocess.run() with a list argument, but on Windows the target CLIs often resolve to .cmd wrappers that are executed through cmd.exe, which interprets metacharacters in the flattened command string. This issue has been patched in version 3.2.0.

Severity

6.7 (Medium)


                        
                          CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H

SSVC

Exploitation: poc Automatable: no Technical Impact: total

CISA Coordinator (v2.0.3)

CWE

CWE-78 - Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

Assigner

GitHub_M

References

2 references

URL	Tags
https://github.com/PrefectHQ/fastmcp/security/adv…	x_refsource_CONFIRM
https://github.com/PrefectHQ/fastmcp/pull/3522	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
jlowin	fastmcp	Affected: < 3.2.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2025-64340",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-04-03T16:11:50.768330Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-04-03T16:12:58.401Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-m8x7-r2rg-vh5g"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "fastmcp",
          "vendor": "jlowin",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 3.2.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "FastMCP is the standard framework for building MCP applications. Prior to version 3.2.0, server names containing shell metacharacters (e.g., \u0026) can cause command injection on Windows when passed to fastmcp install claude-code or fastmcp install gemini-cli. These install paths use subprocess.run() with a list argument, but on Windows the target CLIs often resolve to .cmd wrappers that are executed through cmd.exe, which interprets metacharacters in the flattened command string. This issue has been patched in version 3.2.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "LOCAL",
            "availabilityImpact": "HIGH",
            "baseScore": 6.7,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-78",
              "description": "CWE-78: Improper Neutralization of Special Elements used in an OS Command (\u0027OS Command Injection\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-03T15:16:13.930Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-m8x7-r2rg-vh5g",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-m8x7-r2rg-vh5g"
        },
        {
          "name": "https://github.com/PrefectHQ/fastmcp/pull/3522",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/PrefectHQ/fastmcp/pull/3522"
        }
      ],
      "source": {
        "advisory": "GHSA-m8x7-r2rg-vh5g",
        "discovery": "UNKNOWN"
      },
      "title": "FastMCP has a Command Injection vulnerability - Gemini CLI"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2025-64340",
    "datePublished": "2026-04-03T15:16:13.930Z",
    "dateReserved": "2025-10-30T17:40:52.030Z",
    "dateUpdated": "2026-04-03T16:12:58.401Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

GHSA-M8X7-R2RG-VH5G

Vulnerability from github – Published: 2026-03-31 22:24 – Updated: 2026-04-06 17:37

Summary

FastMCP has a Command Injection vulnerability - Gemini CLI

Details

PoC:

from fastmcp import FastMCP

mcp = FastMCP(name="test&calc")

@mcp.tool
def roll_dice(n_dice: int) -> list[int]:
    """Roll `n_dice` 6-sided dice and return the results."""
    return [random.randint(1, 6) for _ in range(n_dice)]

fastmcp install claude-code server.py   # or: fastmcp install gemini-cli server.py

On Windows, this opens Calculator via the &calc in the server name.

Patched in #3522 by validating server names to reject shell metacharacters.

Severity

6.7 (Medium)


                  
                    CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "fastmcp"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.2.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2025-64340"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-78"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-31T22:24:15Z",
    "nvd_published_at": "2026-04-03T16:16:23Z",
    "severity": "MODERATE"
  },
  "details": "Server names containing shell metacharacters (e.g., `\u0026`) can cause command injection on Windows when passed to `fastmcp install claude-code` or `fastmcp install gemini-cli`. These install paths use `subprocess.run()` with a list argument, but on Windows the target CLIs often resolve to `.cmd` wrappers that are executed through `cmd.exe`, which interprets metacharacters in the flattened command string.\n\nPoC:\n```python\nfrom fastmcp import FastMCP\n\nmcp = FastMCP(name=\"test\u0026calc\")\n\n@mcp.tool\ndef roll_dice(n_dice: int) -\u003e 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```\n\n```\nfastmcp install claude-code server.py   # or: fastmcp install gemini-cli server.py\n```\n\nOn Windows, this opens Calculator via the `\u0026calc` in the server name.\n\nImpact:\nArbitrary command execution with the privileges of the user running `fastmcp install`. Affects Windows hosts where the target CLI (one of claude, gemini) is installed as a `.cmd` wrapper. Does not affect macOS/Linux, and does not affect config-file-based install targets (cursor, goose, mcp-json).\n\nPatched in #3522 by validating server names to reject shell metacharacters.",
  "id": "GHSA-m8x7-r2rg-vh5g",
  "modified": "2026-04-06T17:37:31Z",
  "published": "2026-03-31T22:24:15Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-m8x7-r2rg-vh5g"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jlowin/fastmcp/security/advisories/GHSA-m8x7-r2rg-vh5g"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-64340"
    },
    {
      "type": "WEB",
      "url": "https://github.com/PrefectHQ/fastmcp/pull/3522"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/PrefectHQ/fastmcp"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "FastMCP has a Command Injection vulnerability - Gemini CLI"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

PYSEC-2026-2475

CVE-2025-64340 (GCVE-0-2025-64340)

GHSA-M8X7-R2RG-VH5G

Tags

Sightings

Nomenclature