cobaltosec-corvus 0.9.0

MCP server security testing framework

Corvus

MCP server security testing framework. Tests MCP servers against the OWASP MCP Top 10 — both static analysis and live dynamic probing.

Corvus v0.7.0  MCP Security Scanner
Target     : python my_mcp_server.py
Transport  : stdio
Modules    : tool-poisoning, schema-audit, shadow-tool, auth-audit, log-audit,
             param-injection, info-disclosure, schema-bypass, response-flood, rug-pull

Enumerating surface...
  Tools      : 12
  Resources  : 3
  Prompts    : 2
  Server     : my-server 1.0.0

[MCP01] Tool Poisoning (static)
  [HIGH] Potential prompt injection in description of 'execute_code'

[MCP02] Parameter Injection (dynamic)
  [HIGH] Command injection confirmed in tool 'run_shell', param 'command'
  [MEDIUM] Path traversal accepted in tool 'read_file', param 'path'

...

─── Summary ──────────────────────────────────────────────────────────────────
  CRITICAL  0   HIGH  2   MEDIUM  1   LOW  3   INFO  4
  Session   : corvus-sessions/20260608-143022/

Install

pip install cobaltosec-corvus

Or from source:

git clone https://github.com/CobaltoSec/corvus
cd corvus
pip install -e ".[dev]"

Quick Start

# Scan a stdio MCP server
corvus scan --transport stdio --cmd "python my_server.py"

# Scan an HTTP MCP server
corvus scan --transport http --url http://localhost:8080

# With authentication header
corvus scan --transport http --url http://localhost:8080 --header "Authorization: Bearer token"

# Static analysis only (no live tool calls)
corvus scan --transport stdio --cmd "python my_server.py" --module static

# Specific module
corvus scan --transport stdio --cmd "python my_server.py" --module param-injection

# SARIF output (for CI/CD integration)
corvus scan --transport stdio --cmd "python my_server.py" --sarif

# Fail CI on findings above threshold
corvus scan --transport stdio --cmd "python my_server.py" --fail-on high

# Load config from file
corvus scan --config corvus.toml

# Filter low-confidence findings (0-100)
corvus scan --transport stdio --cmd "python my_server.py" --min-confidence 70

# Capture raw JSON-RPC exchanges
corvus scan --transport stdio --cmd "python my_server.py" --log-requests

# List available modules
corvus list-modules

Batch Scan

Scan multiple MCP servers in one invocation:

# targets.yaml
targets:
  - name: filesystem
    transport: stdio
    cmd: ["npx", "-y", "@modelcontextprotocol/server-filesystem", "/tmp"]

  - name: my-http-server
    transport: http
    url: http://localhost:8080

corvus batch targets.yaml --output-dir results/ --sarif --min-confidence 70

Produces a per-target report.json and a top-level summary.md table.

Modules

Full coverage of OWASP MCP Top 10:

Name	OWASP	Type	What it tests
tool-poisoning	MCP01	static	Hidden instructions, obfuscation, and prompt injection patterns in tool descriptions
param-injection	MCP02	dynamic	Command, path, prompt, and SQL injection payloads per parameter — schema-aware
shadow-tool	MCP03	static	Tool names that shadow built-ins or signal dangerous operations (namespace squatting, trust hijacking)
info-disclosure	MCP04	dynamic	Credentials, filesystem paths, stack traces, and tokens leaked in tool responses
schema-bypass	MCP05	dynamic	Whether tools properly reject inputs that violate their declared schema
rug-pull	MCP06	dynamic	Re-enumerates the server after dynamic testing; diffs against initial snapshot to detect added, removed, or mutated tools
response-flood	MCP07	dynamic	Excessively large or highly repetitive responses that could overflow an LLM context window or inject looping instructions
auth-audit	MCP08	static	Tool names and descriptions suggesting missing, optional, or bypassable authentication
schema-audit	MCP09	static	Weak schema definitions (missing required fields, unconstrained types) that expand the attack surface
log-audit	MCP10	static	Tools that expose or tamper with audit logs — enables anti-forensic techniques or leaks operational data

Module groups

# All modules (default)
--module all

# Static only (no live calls to the server)
--module static

# Dynamic only
--module dynamic

# Individual module
--module param-injection

Transports

stdio

Spawns the server process and communicates via stdin/stdout. Supports any command:

corvus scan --transport stdio --cmd "python server.py"
corvus scan --transport stdio --cmd "npx @modelcontextprotocol/server-filesystem /tmp"
corvus scan --transport stdio --cmd "uvx my-mcp-server --arg value"

HTTP

Connects to a running HTTP/SSE MCP server:

corvus scan --transport http --url http://localhost:8080

# With auth
corvus scan --transport http --url http://localhost:8080 --header "Authorization: Bearer $TOKEN"
corvus scan --transport http --url http://localhost:8080 --header "X-API-Key: secret"

Config File

Create corvus.toml to avoid repeating CLI flags:

[scan]
transport = "stdio"
cmd = "python my_server.py"
modules = "all"
timeout = 30
sarif = false
fail_on = "high"

[scan.headers]
"Authorization" = "Bearer my-token"

Then run:

corvus scan --config corvus.toml

CLI flags override config file values. The --config flag also accepts absolute paths.

CLI Reference

Usage: corvus scan [OPTIONS]

 Scan an MCP server for security vulnerabilities.

Options:
  -t, --transport  TEXT     stdio | http  (overrides config)
  --cmd            TEXT     Command to launch MCP server (stdio)
  --url            TEXT     URL of MCP server (http)
  -m, --module     TEXT     all | static | dynamic | <module-name>  (overrides config)
  -o, --output-dir PATH
  --fail-on        TEXT     Exit 1 if findings at this severity or above
                            (critical|high|medium|low)
  --timeout        INTEGER  Request timeout in seconds (overrides config)
  --sarif                   Also write SARIF 2.1.0 report
  --header         TEXT     HTTP header "Key: Value" (repeatable, for http transport)
  -c, --config     PATH     Path to corvus.toml config file
  --plugin-dir     TEXT     Directory to load external modules from (repeatable)
  --help                    Show this message and exit.

Other commands:

corvus list-modules              # list available modules with OWASP ID and type
corvus list-modules --plugin-dir ./plugins/   # include external plugins
corvus version                   # print version

Output

Each scan creates a session directory under corvus-sessions/<timestamp>/:

corvus-sessions/20260608-143022/
├── report.json     # full structured result
├── report.md       # human-readable with remediation guidance
└── report.sarif    # SARIF 2.1.0 (only when --sarif is passed)

SARIF integration

SARIF output is compatible with GitHub Advanced Security, VS Code SARIF Viewer, and any CI pipeline that consumes SARIF:

# GitHub Actions example
- name: Run Corvus
  run: corvus scan --transport stdio --cmd "python server.py" --sarif --fail-on high

- name: Upload SARIF
  uses: github/codeql-action/upload-sarif@v3
  with:
    sarif_file: corvus-sessions/

CI Integration

# Exit 1 if any CRITICAL findings
corvus scan --transport stdio --cmd "python server.py" --fail-on critical

# Exit 1 if any HIGH or above
corvus scan --transport stdio --cmd "python server.py" --fail-on high

Severity levels (ascending): info → low → medium → high → critical

Plugin System

Add custom modules without modifying Corvus source.

Directory-based plugins

corvus scan --transport stdio --cmd "python server.py" --plugin-dir ./my-modules/

Each .py file in the directory is loaded as a module. The file must define a class that inherits from BaseModule:

from corvus.modules.base import BaseModule, Finding, Severity

class MyCustomModule(BaseModule):
    name = "my-check"
    owasp_id = "MCP-CUSTOM"
    module_type = "static"
    description = "Custom check for my organization"

    async def run(self, surface, transport):
        findings = []
        for tool in surface.tools:
            if "dangerous_pattern" in tool.description:
                findings.append(Finding(
                    rule_id="MY001",
                    tool_name=tool.name,
                    severity=Severity.HIGH,
                    title="Dangerous pattern detected",
                    description=f"Tool '{tool.name}' contains a dangerous pattern.",
                    remediation="Remove or sanitize the pattern.",
                ))
        return findings

Package-based plugins

Register via pyproject.toml entry points:

[project.entry-points."corvus.modules"]
my-check = "my_package.modules.my_check:MyCustomModule"

After pip install my-package, Corvus auto-discovers the module.

Development

git clone https://github.com/CobaltoSec/corvus
cd corvus
pip install -e ".[dev]"
pytest

License

MIT