Fastmcp — the complete, unedited output of the deterministic mcptrustchecker engine v1.13.0, scanned . Every finding, capability tag and score component below is exactly what the engine produced — no AI, no post-processing.
{
"tool": {
"name": "mcptrustchecker",
"version": "1.13.0",
"methodologyVersion": "mcptrustchecker-1.13"
},
"target": {
"id": "fastmcp",
"source": {
"kind": "package",
"origin": "fastmcp"
},
"server": {
"name": "fastmcp"
}
},
"grade": "A",
"score": {
"score": 93,
"threatScore": 100,
"grade": "A",
"band": "A",
"categorySubtotals": {
"injection": 0,
"exfiltration": 0,
"permissions": 0,
"supply-chain": 0,
"network": 0,
"hygiene": 0
},
"vector": [
{
"kind": "client",
"term": "capability-exposure",
"level": "high",
"label": "capability blast radius (high) — client exposure if the model is manipulated",
"appliedPenalty": 6
},
{
"kind": "client",
"term": "verification-discount",
"level": "repo",
"label": "publisher verification (public source) — no provenance, but the source is public and inspectable",
"appliedPenalty": 1
},
{
"kind": "client",
"term": "coverage-honesty",
"level": "source",
"label": "inspection depth (source) — how much of the target the scan could see",
"appliedPenalty": 0
}
],
"gatesFired": [],
"methodologyVersion": "mcptrustchecker-1.13"
},
"capability": {
"level": "high",
"reasons": [
"reads sensitive or local data",
"has a read → egress path (a data-exfiltration surface)",
"can execute shell commands or code"
],
"tags": [
"sensitive-source",
"code-exec"
]
},
"coverage": {
"level": "source",
"inputs": {
"toolSurface": true,
"implementationSource": true,
"packageMetadata": true,
"liveTransport": false
},
"caveats": [
"Tools were statically extracted from the published source (25 recovered), not enumerated from a running server. Tool-poisoning, Unicode-smuggling, capability and toxic-flow analysis ran on this inferred surface, but a mis-parsed registration could be missed or mis-attributed, so tool-derived findings are capped below “confirmed”. To grade the real runtime surface, scan the running server: --command \"npx -y <package>\"."
]
},
"findings": [
{
"ruleId": "MTC-SRC-002",
"title": "Shell/command execution in server code (fastmcp_slim/fastmcp/cli/cli.py)",
"category": "permissions",
"severity": "high",
"confidence": "strong",
"description": "In the server's implementation (`fastmcp_slim/fastmcp/cli/cli.py:55`): Spawning a shell/process is command-execution capability; with unsanitized tool input it is command injection / RCE. This is read from the code itself — not from the tool description — so a poisoned server cannot hide it behind honest-looking metadata.",
"remediation": "Review this call path: confirm it never receives unsanitized tool input, constrain it, or remove it. Treat a server whose code reaches these sinks as high-capability regardless of what its tools claim.",
"location": {
"kind": "server",
"name": "fastmcp_slim/fastmcp/cli/cli.py"
},
"evidence": "try: subprocess.run([cmd, \"--version\"], check=True, capture_output=True) return cmd",
"owasp": "LLM05:2025 Improper Output Handling",
"data": {
"rule": "MTC-SRC-002",
"file": "fastmcp_slim/fastmcp/cli/cli.py",
"line": 55,
"nonRuntime": false
}
},
{
"ruleId": "MTC-SRC-002",
"title": "Shell/command execution in server code (fastmcp_slim/fastmcp/cli/deploy/state.py)",
"category": "permissions",
"severity": "high",
"confidence": "strong",
"description": "In the server's implementation (`fastmcp_slim/fastmcp/cli/deploy/state.py:59`): Spawning a shell/process is command-execution capability; with unsanitized tool input it is command injection / RCE. This is read from the code itself — not from the tool description — so a poisoned server cannot hide it behind honest-looking metadata.",
"remediation": "Review this call path: confirm it never receives unsanitized tool input, constrain it, or remove it. Treat a server whose code reaches these sinks as high-capability regardless of what its tools claim.",
"location": {
"kind": "server",
"name": "fastmcp_slim/fastmcp/cli/deploy/state.py"
},
"evidence": "None: try: subprocess.run( [ \"powershell.exe\", \"-NoLogo\",",
"owasp": "LLM05:2025 Improper Output Handling",
"data": {
"rule": "MTC-SRC-002",
"file": "fastmcp_slim/fastmcp/cli/deploy/state.py",
"line": 59,
"nonRuntime": false
}
},
{
"ruleId": "MTC-SRC-002",
"title": "Shell/command execution in server code (fastmcp_slim/fastmcp/cli/install/claude_code.py)",
"category": "permissions",
"severity": "high",
"confidence": "strong",
"description": "In the server's implementation (`fastmcp_slim/fastmcp/cli/install/claude_code.py:30`): Spawning a shell/process is command-execution capability; with unsanitized tool input it is command injection / RCE. This is read from the code itself — not from the tool description — so a poisoned server cannot hide it behind honest-looking metadata.",
"remediation": "Review this call path: confirm it never receives unsanitized tool input, constrain it, or remove it. Treat a server whose code reaches these sinks as high-capability regardless of what its tools claim.",
"location": {
"kind": "server",
"name": "fastmcp_slim/fastmcp/cli/install/claude_code.py"
},
"evidence": "y: result = subprocess.run( [claude_in_path, \"--version\"], check=True,",
"owasp": "LLM05:2025 Improper Output Handling",
"data": {
"rule": "MTC-SRC-002",
"file": "fastmcp_slim/fastmcp/cli/install/claude_code.py",
"line": 30,
"nonRuntime": false
}
},
{
"ruleId": "MTC-SRC-002",
"title": "Shell/command execution in server code (fastmcp_slim/fastmcp/cli/install/gemini_cli.py)",
"category": "permissions",
"severity": "high",
"confidence": "strong",
"description": "In the server's implementation (`fastmcp_slim/fastmcp/cli/install/gemini_cli.py:27`): Spawning a shell/process is command-execution capability; with unsanitized tool input it is command injection / RCE. This is read from the code itself — not from the tool description — so a poisoned server cannot hide it behind honest-looking metadata.",
"remediation": "Review this call path: confirm it never receives unsanitized tool input, constrain it, or remove it. Treat a server whose code reaches these sinks as high-capability regardless of what its tools claim.",
"location": {
"kind": "server",
"name": "fastmcp_slim/fastmcp/cli/install/gemini_cli.py"
},
"evidence": "orrect path subprocess.run( [gemini_in_path, \"--version\"], check=True,",
"owasp": "LLM05:2025 Improper Output Handling",
"data": {
"rule": "MTC-SRC-002",
"file": "fastmcp_slim/fastmcp/cli/install/gemini_cli.py",
"line": 27,
"nonRuntime": false
}
},
{
"ruleId": "MTC-SRC-002",
"title": "Shell/command execution in server code (fastmcp_slim/fastmcp/cli/install/shared.py)",
"category": "permissions",
"severity": "high",
"confidence": "strong",
"description": "In the server's implementation (`fastmcp_slim/fastmcp/cli/install/shared.py:193`): Spawning a shell/process is command-execution capability; with unsanitized tool input it is command injection / RCE. This is read from the code itself — not from the tool description — so a poisoned server cannot hide it behind honest-looking metadata.",
"remediation": "Review this call path: confirm it never receives unsanitized tool input, constrain it, or remove it. Treat a server whose code reaches these sinks as high-capability regardless of what its tools claim.",
"location": {
"kind": "server",
"name": "fastmcp_slim/fastmcp/cli/install/shared.py"
},
"evidence": "= \"darwin\": subprocess.run([\"open\", url], check=True, capture_output=True) elif sys.platform == \"win",
"owasp": "LLM05:2025 Improper Output Handling",
"data": {
"rule": "MTC-SRC-002",
"file": "fastmcp_slim/fastmcp/cli/install/shared.py",
"line": 193,
"nonRuntime": false
}
},
{
"ruleId": "MTC-SRC-002",
"title": "Shell/command execution in server code (fastmcp_slim/fastmcp/cli/run.py)",
"category": "permissions",
"severity": "high",
"confidence": "strong",
"description": "In the server's implementation (`fastmcp_slim/fastmcp/cli/run.py:309`): Spawning a shell/process is command-execution capability; with unsanitized tool input it is command injection / RCE. This is read from the code itself — not from the tool description — so a poisoned server cannot hide it behind honest-looking metadata.",
"remediation": "Review this call path: confirm it never receives unsanitized tool input, constrain it, or remove it. Treat a server whose code reaches these sinks as high-capability regardless of what its tools claim.",
"location": {
"kind": "server",
"name": "fastmcp_slim/fastmcp/cli/run.py"
},
"evidence": "try: process = subprocess.run(cmd, check=True) sys.exit(process.returncode) except subprocess.Calle",
"owasp": "LLM05:2025 Improper Output Handling",
"data": {
"rule": "MTC-SRC-002",
"file": "fastmcp_slim/fastmcp/cli/run.py",
"line": 309,
"nonRuntime": false
}
},
{
"ruleId": "MTC-SRC-002",
"title": "Shell/command execution in server code (fastmcp_slim/fastmcp/experimental/transforms/code_mode.py)",
"category": "permissions",
"severity": "high",
"confidence": "strong",
"description": "In the server's implementation (`fastmcp_slim/fastmcp/experimental/transforms/code_mode.py:83`): Spawning a shell/process is command-execution capability; with unsanitized tool input it is command injection / RCE. This is read from the code itself — not from the tool description — so a poisoned server cannot hide it behind honest-looking metadata.",
"remediation": "Review this call path: confirm it never receives unsanitized tool input, constrain it, or remove it. Treat a server whose code reaches these sinks as high-capability regardless of what its tools claim.",
"location": {
"kind": "server",
"name": "fastmcp_slim/fastmcp/experimental/transforms/code_mode.py"
},
"evidence": "ox — never with plain ``exec()``. Use ``MontySandboxProvider`` (backed by ``pydantic-monty``) for production worklo",
"owasp": "LLM05:2025 Improper Output Handling",
"data": {
"rule": "MTC-SRC-002",
"file": "fastmcp_slim/fastmcp/experimental/transforms/code_mode.py",
"line": 83,
"nonRuntime": false
}
},
{
"ruleId": "MTC-SRC-002",
"title": "Shell/command execution in server code (fastmcp_slim/fastmcp/utilities/mcp_server_config/v1/environments/uv.py)",
"category": "permissions",
"severity": "high",
"confidence": "strong",
"description": "In the server's implementation (`fastmcp_slim/fastmcp/utilities/mcp_server_config/v1/environments/uv.py:142`): Spawning a shell/process is command-execution capability; with unsanitized tool input it is command injection / RCE. This is read from the code itself — not from the tool description — so a poisoned server cannot hide it behind honest-looking metadata.",
"remediation": "Review this call path: confirm it never receives unsanitized tool input, constrain it, or remove it. Treat a server whose code reaches these sinks as high-capability regardless of what its tools claim.",
"location": {
"kind": "server",
"name": "fastmcp_slim/fastmcp/utilities/mcp_server_config/v1/environments/uv.py"
},
"evidence": "try: subprocess.run( [ \"uv\", \"init\",",
"owasp": "LLM05:2025 Improper Output Handling",
"data": {
"rule": "MTC-SRC-002",
"file": "fastmcp_slim/fastmcp/utilities/mcp_server_config/v1/environments/uv.py",
"line": 142,
"nonRuntime": false
}
},
{
"ruleId": "MTC-SRC-002",
"title": "Shell/command execution in packaging/dev tooling (.claude/skills/release/scripts/changelog_entry.py)",
"category": "permissions",
"severity": "low",
"confidence": "heuristic",
"description": "In a packaging/dev/install script (shipped, but not the server runtime) (`.claude/skills/release/scripts/changelog_entry.py:25`): Spawning a shell/process is command-execution capability; with unsanitized tool input it is command injection / RCE. This is read from the code itself — not from the tool description — so a poisoned server cannot hide it behind honest-looking metadata.",
"remediation": "Review this call path: confirm it never receives unsanitized tool input, constrain it, or remove it. Treat a server whose code reaches these sinks as high-capability regardless of what its tools claim.",
"location": {
"kind": "server",
"name": ".claude/skills/release/scripts/changelog_entry.py"
},
"evidence": "str) -> str: out = subprocess.check_output( [ \"gh\", \"api\", \"-X\",",
"owasp": "LLM05:2025 Improper Output Handling",
"data": {
"rule": "MTC-SRC-002",
"file": ".claude/skills/release/scripts/changelog_entry.py",
"line": 25,
"nonRuntime": true
}
},
{
"ruleId": "MTC-SRC-002",
"title": "Shell/command execution in packaging/dev tooling (examples/diagnostics/server.py)",
"category": "permissions",
"severity": "low",
"confidence": "heuristic",
"description": "In a packaging/dev/install script (shipped, but not the server runtime) (`examples/diagnostics/server.py:30`): Spawning a shell/process is command-execution capability; with unsanitized tool input it is command injection / RCE. This is read from the code itself — not from the tool description — so a poisoned server cannot hide it behind honest-looking metadata.",
"remediation": "Review this call path: confirm it never receives unsanitized tool input, constrain it, or remove it. Treat a server whose code reaches these sinks as high-capability regardless of what its tools claim.",
"location": {
"kind": "server",
"name": "examples/diagnostics/server.py"
},
"evidence": "_tracing.py\" proc = subprocess.Popen( [ \"uv\", \"run\", str(run_with_tracin",
"owasp": "LLM05:2025 Improper Output Handling",
"data": {
"rule": "MTC-SRC-002",
"file": "examples/diagnostics/server.py",
"line": 30,
"nonRuntime": true
}
},
{
"ruleId": "MTC-SUP-012",
"title": "Package has no license",
"category": "hygiene",
"severity": "info",
"confidence": "strong",
"description": "\"fastmcp\" has no declared license. This is a legal/reuse concern, not a security finding.",
"location": {
"kind": "package",
"name": "fastmcp"
}
}
],
"toxicFlows": [],
"capabilities": [
{
"tool": "save_contact",
"tags": [],
"reasons": {}
},
{
"tool": "save",
"tags": [],
"reasons": {}
},
{
"tool": "store_files",
"tags": [],
"reasons": {}
},
{
"tool": "list_files",
"tags": [
"sensitive-source"
],
"reasons": {
"sensitive-source": [
"keyword \"list_files\""
]
}
},
{
"tool": "read_file",
"tags": [
"sensitive-source"
],
"reasons": {
"sensitive-source": [
"keyword \"read_file\""
]
}
},
{
"tool": "submit_form",
"tags": [],
"reasons": {}
},
{
"tool": "echo_tool",
"tags": [],
"reasons": {}
},
{
"tool": "get_info",
"tags": [],
"reasons": {}
},
{
"tool": "get_my_emails",
"tags": [],
"reasons": {}
},
{
"tool": "my_tool",
"tags": [],
"reasons": {}
},
{
"tool": "my_task",
"tags": [],
"reasons": {}
},
{
"tool": "store_data",
"tags": [],
"reasons": {}
},
{
"tool": "long_running_task",
"tags": [],
"reasons": {}
},
{
"tool": "log_progress",
"tags": [],
"reasons": {}
},
{
"tool": "introspect",
"tags": [],
"reasons": {}
},
{
"tool": "get_client_ip",
"tags": [],
"reasons": {}
},
{
"tool": "get_auth_type",
"tags": [],
"reasons": {}
},
{
"tool": "get_user_id",
"tags": [],
"reasons": {}
},
{
"tool": "add_expense",
"tags": [],
"reasons": {}
},
{
"tool": "greet",
"tags": [],
"reasons": {}
},
{
"tool": "custom_name",
"tags": [],
"reasons": {}
},
{
"tool": "remember",
"tags": [],
"reasons": {}
},
{
"tool": "add",
"tags": [],
"reasons": {}
},
{
"tool": "multiply",
"tags": [],
"reasons": {}
},
{
"tool": "run_query",
"tags": [],
"reasons": {}
}
],
"surfaceDigest": "d0ac4b88ab2b9f7c3e2f1625209d7000133a6188a7a703fa54bf38f801ebcba6",
"stats": {
"tools": 25,
"prompts": 0,
"resources": 0,
"findingsBySeverity": {
"critical": 0,
"high": 8,
"medium": 0,
"low": 2,
"info": 1
}
}
}