code-security-mcp

A security MCP server for AI coding agents. It gives Claude Code, Cursor, and other agents real security findings while they write, not after — and each language is analyzed by its best native security tool, not one generic scanner stretched across everything.

A specialist, not a generalist. Kotlin is analyzed by detekt with a 216-rule, framework-aware ruleset (Spring, WebFlux, Ktor, Quarkus, Micronaut, Vert.x); Java by SpotBugs + FindSecBugs; Python by Bandit; C# by the Roslyn security analyzers; JS/TS by ESLint + eslint-plugin-security — each the established native security analyzer for its language, routed automatically.

New languages arrive as their own native analyzer — never a single lowest-common-denominator scanner.

Quickstart

git clone https://github.com/JasminGuberinic/code-security-mcp
cd code-security-mcp
python3 -m venv .venv && .venv/bin/pip install -e ".[python]"

# Download the analyzers into an isolated cache (nothing global is touched):
./scripts/setup.sh                              # Kotlin + Java
./scripts/setup.sh --with-dotnet --with-eslint  # + C# and JS/TS (optional)

The script prints the claude mcp add … command to paste. Python works out of the box — the [python] extra installs Bandit.

Why

Generic assistants and multi-language scanners are shallow on framework idioms — they don't know that a @GetMapping is missing @PreAuthorize, that a WebClient trusts all certificates, or that a Vert.x cookie isn't HttpOnly. This server wraps a 216-rule, framework-aware analyzer (the kotlin-security-scanner detekt ruleset) and exposes it to agents through three tools.

Design principle: each language is handled by its best native security analyzer — routed automatically — never a single lowest-common-denominator generic scanner.

Languages

Language	Analyzer	Analyzes
Kotlin	detekt + the 216-rule framework-aware ruleset	source (.kt, .kts)
Java	SpotBugs + FindSecBugs	compiled bytecode — point at the project root (it finds build/classes, target/classes, …), a classes dir, or a .jar (build first)
Python	Bandit	source (.py) — no build, just pip install
C#	Roslyn security analyzers	builds the project — point at a .sln, .csproj, or its directory
JavaScript / TypeScript	ESLint + eslint-plugin-security	source (.js, .ts, .jsx, .tsx, …)

Tools

Tool	What it does
security_scan(path)	Scan a file/directory (Kotlin, Java, Python, C#, or JS/TS) and return every security finding (rule, line, severity, CWE).
review_diff(diff)	Review a unified diff and flag only the issues the change introduces — a pre-commit self-check.
secure_pattern(task, framework?)	Get the vetted secure way to do a risky task — before writing it.

For Kotlin, security_scan returns security findings only — detekt's built-in style/complexity rules are switched off, so the agent gets signal, not noise.

Example

"What's the secure way to create a session cookie in Vert.x?"

// secure_pattern(task = "create a session cookie", framework = "vertx")  →  CWE-614
val cookie = Cookie.cookie("session", token)
    .setSecure(true)      // only sent over HTTPS
    .setHttpOnly(true)    // hidden from JavaScript
    .setSameSite(CookieSameSite.STRICT)
response.addCookie(cookie)

Architecture

Clean, hexagonal (ports & adapters). Dependencies point inward; the domain knows nothing about detekt or MCP.

server.py            MCP surface + composition root   (knows MCP)
   │
application/         use cases: scan / review_diff / secure_pattern
   │
domain/              Finding, ScanResult, ports         (pure vocabulary)
   ↑ implemented by
adapters/            DetektAnalyzer, JavaAnalyzer, RoutingAnalyzer,
                     SARIF & diff parsers, pattern catalog

A RoutingAnalyzer sends each target to the analyzers that support it, so the use cases treat "one language" and "many" identically. Adding a language = one new adapter implementing the same LanguageAnalyzer port — the domain and use cases do not change.

Requirements

• Python 3.11+
• Kotlin: a JDK + the detekt CLI jar + the ruleset jar(s)
• Java: a JDK + the SpotBugs jar + the FindSecBugs plugin jar
• Python: Bandit (pip install "code-security-mcp[python]") — no JDK, no jars
• C#: the .NET SDK (its Roslyn security analyzers are built in)
• JS/TS: Node.js + ESLint with eslint-plugin-security (and typescript-eslint)

Each analyzer is optional and enabled independently — configure only the languages you need. (Python auto-enables whenever Bandit is installed.)

Configuration

./scripts/setup.sh fills these in for you and prints the ready-to-paste command; the reference below is for when you want to point at your own tools. The server locates its tools through environment variables:

Variable	Meaning
KSM_JAVA	Path to the java executable (shared)
KSM_DETEKT_CLI_JAR	Kotlin: detekt CLI (-all) jar
KSM_PLUGIN_JARS	Kotlin: comma-separated ruleset jar(s)
KSM_DETEKT_CONFIG	Kotlin: (optional) path to a detekt.yml
KSM_SPOTBUGS_JAR	Java: SpotBugs engine jar
KSM_FINDSECBUGS_JARS	Java: comma-separated plugin jar(s) (FindSecBugs)
KSM_JAVA_AUXCLASSPATH	Java: (optional) comma-separated dependency jars/dirs for more accurate analysis
KSM_DOTNET_ROOT	C#: root of the .NET SDK install
KSM_NUGET_PACKAGES	C#: (optional) NuGet cache dir (keeps restores isolated)
KSM_DOTNET_CLI_HOME	C#: (optional) dotnet CLI home dir (keeps state isolated)
KSM_ESLINT_BIN	JS/TS: path to the ESLint executable
KSM_ESLINT_CONFIG	JS/TS: path to the security flat config (see configs/)

Python needs no variables — install Bandit and it is used automatically.

Use with Claude Code

claude mcp add code-security -s user \
  -e KSM_JAVA=/path/to/java \
  -e KSM_DETEKT_CLI_JAR=/path/to/detekt-cli-<ver>-all.jar \
  -e KSM_PLUGIN_JARS=/path/to/scanner-core.jar,/path/to/scanner-spring-boot.jar,... \
  -- /path/to/.venv/bin/code-security-mcp

Then ask the agent, e.g. "run security_scan on src/Main.kt" or "review_diff on my staged changes".

Development

python3 -m venv .venv
.venv/bin/pip install -e ".[dev]"
.venv/bin/pytest

The test suite is hermetic — it uses fake analyzers and hand-built SARIF / diff / Bandit-JSON fixtures, so it needs no external analyzer (JDK, detekt, SpotBugs, or Bandit) to run.

Roadmap

Each new language arrives as its own native, framework-aware analyzer adapter (never a generic multi-language scanner):

• ✅ Kotlin — detekt + the 216-rule framework-aware ruleset.
• ✅ Java — SpotBugs + FindSecBugs.
• ✅ Python — Bandit.
• ✅ C# — Roslyn security analyzers.
• ✅ JavaScript / TypeScript — ESLint + eslint-plugin-security.
• Deeper C# via Security Code Scan (taint analysis).
• Zero-setup: auto-resolve the analyzer runtimes and rulesets.

License

MIT — see LICENSE.

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_{Keywords: MCP server, Model Context Protocol, Kotlin security, JVM security, SAST, static analysis, detekt, Spring Security, AI coding agent, Claude Code, Cursor, secure coding.}