Relay Shell MCP Server
relay-shell
PyPI
v0.3.0
Published by rmednitzer — no publish provenance, so origin is unverified, but the source is public: the repository link below is self-declared yet readable, so you can inspect the code before adopting it.
A highly reliable, maximally capable MCP server for complete shell and SSH mastery: a governed relay in the shell/SSH path.
The grade answers one question — how safe is this server for you to adopt — so it is computed in two auditable stages. Nothing below is an opinion or an LLM's guess; every line is a real term the deterministic engine applied, and the same input always yields the same number.
1. Threat score — 100 − 1.2 = 99. What the published surface and source actually contain:
| Points | What was found | Category |
|---|---|---|
| −1.2 | Hardcoded AWS access key id in test/example/packaging MTC-SRC-008 | exfiltration |
2. Client adoption risk — 99 − 7 = 92. Three small, subtract-only factors that reflect your risk in adopting it — a clean scan proves less on a powerful, unverified or barely-inspectable package, so the grade says so plainly:
| Points | Adoption-risk factor |
|---|---|
| −6 | capability blast radius (high) — client exposure if the model is manipulated |
| −1 | publisher verification (public source) — no provenance, but the source is public and inspectable |
Capability observations and info notes are shown under Findings but never scored.
Open any row's finding below for the file, line and evidence behind a deduction.
Findings 16
high Tool "shell_exec" exposes command/code executionMTC-CAP-001
Tool "shell_exec" appears to run shell commands or evaluate code (keyword "exec" in tool name). Arbitrary execution driven by model input is one of the most dangerous MCP capabilities; combined with any untrusted input it becomes RCE.
Fix: Sandbox execution, allowlist commands/arguments, and never pass model output to a shell unescaped.
Location: tool shell_exec
high Tool "shell_script" exposes command/code executionMTC-CAP-001
Tool "shell_script" appears to run shell commands or evaluate code (keyword "shell" in tool name). Arbitrary execution driven by model input is one of the most dangerous MCP capabilities; combined with any untrusted input it becomes RCE.
Fix: Sandbox execution, allowlist commands/arguments, and never pass model output to a shell unescaped.
Location: tool shell_script
high Tool "shell_spawn" exposes command/code executionMTC-CAP-001
Tool "shell_spawn" appears to run shell commands or evaluate code (keyword "shell" in tool name). Arbitrary execution driven by model input is one of the most dangerous MCP capabilities; combined with any untrusted input it becomes RCE.
Fix: Sandbox execution, allowlist commands/arguments, and never pass model output to a shell unescaped.
Location: tool shell_spawn
high Tool "ssh_exec" exposes command/code executionMTC-CAP-001
Tool "ssh_exec" appears to run shell commands or evaluate code (keyword "exec" in tool name). Arbitrary execution driven by model input is one of the most dangerous MCP capabilities; combined with any untrusted input it becomes RCE.
Fix: Sandbox execution, allowlist commands/arguments, and never pass model output to a shell unescaped.
Location: tool ssh_exec
high Tool "ssh_spawn" exposes command/code executionMTC-CAP-001
Tool "ssh_spawn" appears to run shell commands or evaluate code (keyword "spawn" in tool name). Arbitrary execution driven by model input is one of the most dangerous MCP capabilities; combined with any untrusted input it becomes RCE.
Fix: Sandbox execution, allowlist commands/arguments, and never pass model output to a shell unescaped.
Location: tool ssh_spawn
high Shell/command execution in server code (src/relay_shell/sessions.py)MTC-SRC-002
In the server's implementation (`src/relay_shell/sessions.py:89`): 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.
Evidence: assmethod async def spawn( cls, argv: list[str], *, cwd: str | None, env: di
Fix: 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: server src/relay_shell/sessions.py
medium Untrusted input can drive an external actionMTC-FLOW-005
Untrusted-input tools ([ssh_download]) co-exist with external-action tools ([shell_exec, shell_script, shell_spawn, ssh_exec, ssh_spawn]). A prompt injection could cause unwanted external actions, though no direct sensitive-data leak path was found.
Evidence: untrusted [ssh_download] → sinks [shell_exec, shell_script, shell_spawn, ssh_exec, ssh_spawn]
Fix: Require confirmation for state-changing/egress actions triggered after processing untrusted content.
Location: flow ssh_download → shell_exec
low Hardcoded AWS access key id in test/example/packaging (tests/test_patterns.py)MTC-SRC-008
A hardcoded AWS access key id (a live-looking credential hardcoded in shipped code) appears in `tests/test_patterns.py:332`. Verify whether this is a real credential; if so, remove and rotate it.
Evidence: AWS access key id: AKIA…(redacted)
Fix: Remove the secret, rotate it, and load credentials from the environment or a secret store.
Location: server tests/test_patterns.py
low Mutating tool "shell_exec" declares no destructiveHintMTC-CAP-005
Tool "shell_exec" can mutate/egress but declares no destructiveHint. Clients that don't default to spec-safe behavior may not prompt before running it.
Fix: Declare accurate annotations, and gate destructive tools on user confirmation regardless.
Location: tool shell_exec
low Mutating tool "shell_script" declares no destructiveHintMTC-CAP-005
Tool "shell_script" can mutate/egress but declares no destructiveHint. Clients that don't default to spec-safe behavior may not prompt before running it.
Fix: Declare accurate annotations, and gate destructive tools on user confirmation regardless.
Location: tool shell_script
low Mutating tool "shell_spawn" declares no destructiveHintMTC-CAP-005
Tool "shell_spawn" can mutate/egress but declares no destructiveHint. Clients that don't default to spec-safe behavior may not prompt before running it.
Fix: Declare accurate annotations, and gate destructive tools on user confirmation regardless.
Location: tool shell_spawn
low Mutating tool "ssh_exec" declares no destructiveHintMTC-CAP-005
Tool "ssh_exec" can mutate/egress but declares no destructiveHint. Clients that don't default to spec-safe behavior may not prompt before running it.
Fix: Declare accurate annotations, and gate destructive tools on user confirmation regardless.
Location: tool ssh_exec
low Mutating tool "ssh_spawn" declares no destructiveHintMTC-CAP-005
Tool "ssh_spawn" can mutate/egress but declares no destructiveHint. Clients that don't default to spec-safe behavior may not prompt before running it.
Fix: Declare accurate annotations, and gate destructive tools on user confirmation regardless.
Location: tool ssh_spawn
low Shell/command execution in packaging/dev tooling (tests/test_main.py)MTC-SRC-002
In a packaging/dev/install script (shipped, but not the server runtime) (`tests/test_main.py:35`): 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.
Evidence: e(env_extra) return subprocess.run( [sys.executable, "-m", "relay_shell", *args], capture_output=Tru
Fix: 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: server tests/test_main.py
low Shell/command execution in packaging/dev tooling (tests/test_sessions.py)MTC-SRC-002
In a packaging/dev/install script (shipped, but not the server runtime) (`tests/test_sessions.py:170`): 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.
Evidence: leaked once per failed spawn (e.g. a typo'd binary). """ argv = ["/nonexistent-relay-shell-binary"] # Warm-
Fix: 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: server tests/test_sessions.py
low Shell/command execution in packaging/dev tooling (tests/test_verifier.py)MTC-SRC-002
In a packaging/dev/install script (shipped, but not the server runtime) (`tests/test_verifier.py:139`): 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.
Evidence: rocess[str]: return subprocess.run( [sys.executable, "-m", "relay_shell", *args], capture_output=Tru
Fix: 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: server tests/test_verifier.py
Tools 22
Each tool and what it can reach — statically extracted from the published source.
shell_execruns code / shellshell_scriptruns code / shellshell_spawnruns code / shellssh_downloadingests untrusted inputssh_execruns code / shellssh_spawnruns code / shellaudit_tailno sensitive capabilityoperation_confirmno sensitive capabilityserver_infono sensitive capabilitysession_killno sensitive capability
Show 12 more tools ↓
session_listno sensitive capabilitysession_recvno sensitive capabilitysession_resizeno sensitive capabilitysession_sendno sensitive capabilityssh_checkno sensitive capabilityssh_fanoutno sensitive capabilityssh_forwardno sensitive capabilityssh_forward_closeno sensitive capabilityssh_forward_listno sensitive capabilityssh_hostsno sensitive capabilityssh_keyscanno sensitive capabilityssh_uploadno sensitive capability
Toxic flows 1
Cross-tool combinations that form a data-exfiltration primitive (untrusted input → sensitive source → external sink).
What this scan could not see
- Tools were statically extracted from the published source (22 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>".
Versions 1
Scan history per published version. The engine is deterministic — the same version always yields the same score, so a changed score means the package itself changed.
| Version | Score | Findings | Engine | Scanned |
|---|---|---|---|---|
v0.3.0 latest |
A 92/100 | 16 | 1.13.0 | 2026-08-25 |
Embed this score
Show this server's live Trust Score in your README, docs or website. The badge is served straight from the registry and updates automatically after every rescan — no API key needed. It links back to this page, so anyone who sees the grade can also read the findings behind it instead of taking a number on faith.
Verify this score yourself
The score above is reproducible: the same package version always yields the same result. Run it locally or over the free API — no account, no LLM, fully deterministic.
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