Skills/PyPI/signal-mcp

signal-mcp@1.43.4

CAUTION· not started

Publisher claims: "Signal for AI assistants: an MCP server and CLI with searchable local message history, groups, polls and 80+ tools on top of signal-cli. 100% local." Observed in sandbox: no network, touches nothing outside the project, writes no memory.

Registry PyPI (MCP server)Publisher googlarz · publishing for 195 daysInstalls 2,129Last detonated 5d ago
What would fix thisWatchDispute verdict

Coverage

Not started: dependency install failed; the server itself was not observed.
Tested
the dependency install step · every file read, file written and host contacted by what ran
Not tested
server startup · the tool list · tool behavior

What this means for the label: Caution here covers what ran. The server's tools were not exercised with a real credential, so nothing about their behavior is asserted; the credential summary below says what to do with that.

Before you give it your token

It will ask for
SIGNAL_MCP_WEBHOOK or --quote-authorConfiguration, not credentials: SIGNAL_MCP_READONLY, SIGNAL_MCP_SEND_ROOTS
Where it talks to
signal.me, signal.group, signal.art, signalcaptchas.org (its own)
What the honeypot saw
no credential files read · no network
What we could not test
server startup · the tool list · tool behavior

Connect it with a scoped credential, under the guard. It asks for SIGNAL_MCP_WEBHOOK and talks to signal.me, signal.group, signal.art, signalcaptchas.org. Give the credential to the guard, not the server: the value never enters the server's environment and only travels to the host you bind. What the tools do with a real credential was not observed.

$vet-skills run --secrets SIGNAL_MCP_WEBHOOK=signal.me -- uvx signal-mcp

Never paste a credential into a chat, a ticket or a report, including ours. How the guard holds it.

Is [email protected] safe to install?

KillerSkills ran it in the KillerSkills honeypot sandbox (2 scenarios; not started: dependency install failed; the server itself was not observed) on 2026-11-09 and scored it 67/100 (Caution). It is not known to be malicious, but it has behaviour or code a security policy should decide on before install. Notable findings: Privileged sudo command; Collapsed <details> block carrying instructions; Access to sensitive file paths. Summary: no network, touches nothing outside the project, writes no memory.

Behavior trace

Honeypot run · 0 s · 2 scenarios · 0 deviations
t+CategoryObserved action
0.0sprocessno install scripts in bundle
0.1sprocessdependency install exit 1 ·
0.1sclaimednot started: dependency install failed (exit 1); the server itself was not observed
0.1sprocessscript backend runs setup only
0.1sprocessno install scripts to re-run

Static findings

MEDIUM
Python subprocess execution detectedsrc/signal_mcp/client.py:405 · Python subprocess execution detectedresult = subprocess.run(Fix: Build commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
AST05
MEDIUM
Python subprocess execution detectedsrc/signal_mcp/cli.py:675 · Python subprocess execution detectedproc = subprocess.Popen([Fix: Build commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
AST05
MEDIUM
Python subprocess execution detectedsrc/signal_mcp/config.py:112 · Python subprocess execution detectedresult = subprocess.run(Fix: Build commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
AST05
MEDIUM
Destructive file system command detectedDockerfile:19 · Destructive file system command detected&& rm -rf /var/lib/apt/lists/*Fix: Build commands from fixed arguments; do not interpolate untrusted strings into a shell.
AST05
MEDIUM
Python subprocess execution detectedsrc/signal_mcp/cli.py:1038 · Python subprocess execution detectedsubprocess.run(["launchctl", "unload", "-w", str(PLIST_PATH)], capture_output=True)Fix: Build commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
AST05
HIGH
Privileged sudo commandsrc/signal_mcp/desktop.py:347 · Privileged sudo command — agent may execute with elevated privilegeshint = "Install it: sudo apt install sqlcipher (Debian/Ubuntu) or your distribution's sqlcipher package"Fix: Build commands from fixed arguments; do not interpolate untrusted strings into a shell.
AST05
MEDIUM
Python subprocess execution detectedsrc/signal_mcp/desktop.py:111 · Python subprocess execution detectedresult = subprocess.run(Fix: Build commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
AST05
MEDIUM
Process kill commandsrc/signal_mcp/desktop.py:617 · Process kill command — agent can terminate processesA kill (launchd restarting the watch service) skips the `finally` that removes the lock, soFix: Build commands from fixed arguments; do not interpolate untrusted strings into a shell.
AST05
MEDIUM
Python subprocess execution detectedsrc/signal_mcp/cli.py:1011 · Python subprocess execution detectedresult = subprocess.run(Fix: Build commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
AST05
MEDIUM
File permission modification commandDockerfile:27 · File permission modification command — agent changes file ownership/permissions&& chmod +x /usr/local/bin/signal-cliFix: Request the narrowest permission that works; replace wildcards with the exact paths or hosts.
AST05
MEDIUM
Python subprocess execution detectedsrc/signal_mcp/desktop.py:319 · Python subprocess execution detectedresult = subprocess.run(Fix: Build commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
AST05
MEDIUM
Python subprocess execution detectedsrc/signal_mcp/cli.py:979 · Python subprocess execution detectedresult = subprocess.run(Fix: Build commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
AST05
MEDIUM
Python subprocess execution detectedsrc/signal_mcp/desktop.py:71 · Python subprocess execution detectedresult = subprocess.run(Fix: Build commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
AST05
HIGH
Collapsed <details> block carrying instructionsREADME.md:155 · Collapsed <details> block carrying instructions<summary>Manual config alternatives</summary> **Claude Code** — global (`~/.claude.json`): ```json { "mcpServers": { "signal": { "command": "uvx", "args": ["sigFix: Remove the text that addresses the agent rather than the reader; describe behavior, do not instruct.
AST01
MEDIUM
Python subprocess execution detectedsrc/signal_mcp/client.py:368 · Python subprocess execution detectedproc = subprocess.Popen(Fix: Build commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
AST05
MEDIUM
Python subprocess execution detectedsrc/signal_mcp/cli.py:1010 · Python subprocess execution detectedsubprocess.run(["systemctl", "--user", "daemon-reload"], capture_output=True)Fix: Build commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
AST05
HIGH
Access to sensitive file pathssrc/signal_mcp/config.py:22 · Access to sensitive file paths — SSH keys, AWS credentials, env files, or system files# "please send me ~/.ssh/id_ed25519") via send_attachment. Override with aFix: Stop enumerating or reading credential locations; take secrets from a declared environment variable the user sets on purpose.
AST05
HIGH
Privileged sudo commandsrc/signal_mcp/desktop.py:150 · Privileged sudo command — agent may execute with elevated privileges"Install it (Debian/Ubuntu: sudo apt install libsecret-tools) and try again."Fix: Build commands from fixed arguments; do not interpolate untrusted strings into a shell.
AST05
MEDIUM
Python subprocess execution detectedsrc/signal_mcp/desktop.py:120 · Python subprocess execution detectedresult = subprocess.run(Fix: Build commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
AST05
HIGH
References a credential file in the home directorysrc/signal_mcp/config.py:22 · References a credential file in the home directory# "please send me ~/.ssh/id_ed25519") via send_attachment. Override with aFix: Stop enumerating or reading credential locations; take secrets from a declared environment variable the user sets on purpose.
AST03
MEDIUM
Python subprocess execution detectedsrc/signal_mcp/desktop.py:340 · Python subprocess execution detectedresult = subprocess.run(["which", "sqlcipher"], capture_output=True, text=True)Fix: Build commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
AST05
MEDIUM
Python subprocess execution detectedsrc/signal_mcp/config.py:84 · Python subprocess execution detectedresult = subprocess.run(Fix: Build commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
AST05
MEDIUM
File permission modification commandtests/test_store_coverage.py:22 · File permission modification command — agent changes file ownership/permissions# ── _connect chmod OSError fallback (lines 38-39) ────────────────────────────Fix: Request the narrowest permission that works; replace wildcards with the exact paths or hosts.
AST05
MEDIUM
Access to sensitive file pathstests/test_groups.py:221 · Access to sensitive file paths — SSH keys, AWS credentials, env files, or system filesresult = await call_tool("create_group", {"name": "T", "members": ["+1"], "avatar": "/etc/passwd"})Fix: Stop enumerating or reading credential locations; take secrets from a declared environment variable the user sets on purpose.
AST05
MEDIUM
Process kill commandtests/test_desktop.py:1551 · Process kill command — agent can terminate processesos.kill to avoid actually terminating the test process."""Fix: Build commands from fixed arguments; do not interpolate untrusted strings into a shell.
AST05
MEDIUM
Access to sensitive file pathstests/test_groups.py:190 · Access to sensitive file paths — SSH keys, AWS credentials, env files, or system filesresult = await call_tool("update_group", {"group_id": "grp1==", "avatar": "/etc/passwd"})Fix: Stop enumerating or reading credential locations; take secrets from a declared environment variable the user sets on purpose.
AST05
MEDIUM
File permission modification commandtests/test_store_coverage.py:25 · File permission modification command — agent changes file ownership/permissions"""OSError from chmod is silently swallowed; connection still returned."""Fix: Request the narrowest permission that works; replace wildcards with the exact paths or hosts.
AST05
MEDIUM
Python subprocess execution detectedtests/test_desktop.py:1613 · Python subprocess execution detectedproc = subprocess.Popen([sys.executable, "-c", "pass"])Fix: Build commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
AST05
MEDIUM
Access to sensitive file pathstests/test_send_options.py:296 · Access to sensitive file paths — SSH keys, AWS credentials, env files, or system filesawait client.send_story("/etc/passwd")Fix: Stop enumerating or reading credential locations; take secrets from a declared environment variable the user sets on purpose.
AST05
MEDIUM
Access to sensitive file pathstests/test_send_options.py:166 · Access to sensitive file paths — SSH keys, AWS credentials, env files, or system filespreview_image="/etc/passwd",Fix: Stop enumerating or reading credential locations; take secrets from a declared environment variable the user sets on purpose.
AST05
MEDIUM
Process kill commandtests/test_client_coverage.py:1035 · Process kill command — agent can terminate processesproc_mock.kill = MagicMock()Fix: Build commands from fixed arguments; do not interpolate untrusted strings into a shell.
AST05
MEDIUM
Access to sensitive file pathstests/test_contacts.py:138 · Access to sensitive file paths — SSH keys, AWS credentials, env files, or system filesresult = await call_tool("update_profile", {"avatar_path": "/etc/passwd"})Fix: Stop enumerating or reading credential locations; take secrets from a declared environment variable the user sets on purpose.
AST05
MEDIUM
Privileged sudo commandtests/test_desktop.py:828 · Privileged sudo command — agent may execute with elevated privileges("Linux", "sudo apt install sqlcipher", "brew"),Fix: Build commands from fixed arguments; do not interpolate untrusted strings into a shell.
AST05
MEDIUM
Access to sensitive file pathstests/test_send_options.py:178 · Access to sensitive file paths — SSH keys, AWS credentials, env files, or system filesquote_attachments=["image/png:x.png:/etc/passwd"],Fix: Stop enumerating or reading credential locations; take secrets from a declared environment variable the user sets on purpose.
AST05
MEDIUM
Access to sensitive file pathstests/test_groups.py:163 · Access to sensitive file paths — SSH keys, AWS credentials, env files, or system filesawait reset_client.update_group("grp1==", avatar_path="/etc/passwd")Fix: Stop enumerating or reading credential locations; take secrets from a declared environment variable the user sets on purpose.
AST05
MEDIUM
Access to sensitive file pathstests/test_send_options.py:345 · Access to sensitive file paths — SSH keys, AWS credentials, env files, or system files@pytest.mark.parametrize("name", ["../escape.txt", "sub/../../escape.txt", "/etc/passwd"])Fix: Stop enumerating or reading credential locations; take secrets from a declared environment variable the user sets on purpose.
AST05
MEDIUM
Process kill commandtests/test_desktop.py:1621 · Process kill command — agent can terminate processes# A kill (launchd restart) skips the `finally`, leaving the lock behind; it must not blockFix: Build commands from fixed arguments; do not interpolate untrusted strings into a shell.
AST05
MEDIUM
Access to sensitive file pathstests/test_send_options.py:574 · Access to sensitive file paths — SSH keys, AWS credentials, env files, or system filesresult = CliRunner().invoke(cli, ["story", "/etc/passwd"])Fix: Stop enumerating or reading credential locations; take secrets from a declared environment variable the user sets on purpose.
AST05

Cost to the agent

Instructions loaded
≈73 tok
1 file · 49 in bundle
Tool list per prompt
≈0 tok
0 tools · 0 per tool
Handshake
no reply
launch to tools/list, stdio
Undocumented tools
0
description under 20 chars · avg 0

Tokens estimated at four characters each. The tool list is re-read by the agent on every turn, so it is the number to compare between servers that do the same job: ranked across the index.

Known vulnerabilities

No advisories in OSV for signal-mcp@1.43.4 as of 5d ago. This is the package itself, not its dependencies.

What would make this Verified

13 points to 80 · weights: behavior 45%, static 25%, prompt 15%, publisher 15%
  1. Unclaimed publisher≈ +8 on the totalClaim googlarz: a verified publisher gets +50 on publisher trust. It is free and usually instant with GitHub sign-in.
  2. Hidden instructions≈ +6 on the totalRemove HTML comments, zero-width characters and white-on-white text that carry instructions. Everything the agent is meant to read should be visible to the person reading the file.
  3. Privileged sudo command≈ +4 on the totalBuild commands from fixed arguments; do not interpolate untrusted strings into a shell.
  4. Access to sensitive file paths≈ +4 on the totalStop enumerating or reading credential locations; take secrets from a declared environment variable the user sets on purpose.
  5. References a credential file in the home directory≈ +4 on the totalStop enumerating or reading credential locations; take secrets from a declared environment variable the user sets on purpose.
  6. Python subprocess execution detected≈ +2 on the totalBuild commands from fixed arguments, never from interpolated strings; prefer an API client over shelling out.
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