Summary

The setconfigvalue() API endpoint allows users with the non-admin SETTINGS permission to modify any configuration option without restriction. The reconnect.script config option controls a file path that is passed directly to subprocess.run() in the thread manager's reconnect logic. A SETTINGS user can set this to any executable file on the system, achieving Remote Code Execution. The only validation in setconfigvalue() is a hardcoded check for general.storagefolder — all other security-critical settings including reconnect.script are writable without any allowlist or path restriction.

Details

The vulnerability chain spans two components:

1. Unrestricted config write — src/pyload/core/api/init.py:210-243

python @permission(Perms.SETTINGS) @post def setconfigvalue(self, category: str, option: str, value: Any, section: str = "core") -> None: self.pyload.addonmanager.dispatchevent( "configchanged", category, option, value, section ) if section == "core": if category == "general" and option == "storagefolder": # Forbid setting the download folder inside dangerous locations # ... validation only for storagefolder ... return

self.pyload.config.set(category, option, value) # No validation for any other option

The Perms.SETTINGS permission (value 128) is a non-admin permission flag. The only hardcoded validation is for general.storagefolder. The reconnect.script option is written directly to config with no path validation, allowlist, or sanitization.

2. Arbitrary script execution — src/pyload/core/managers/threadmanager.py:157-199

python def tryreconnect(self): if not ( self.pyload.config.get("reconnect", "enabled") and self.pyload.api.istimereconnect() ): return False

# ... checks if active downloads want reconnect ...

reconnectscript = self.pyload.config.get("reconnect", "script") if not os.path.isfile(reconnectscript): self.pyload.config.set("reconnect", "enabled", False) self.pyload.log.warning(self.("Reconnect script not found!")) return

# ... reconnect logic ...

try: subprocess.run(reconnectscript) # Executes attacker-controlled path except Exception: # ...

The reconnectscript value comes directly from config. The only check is os.path.isfile() — the file must exist but there is no allowlist, no path restriction, and no signature verification.

3. Attacker also controls timing via same SETTINGS permission

The attacker can set reconnect.enabled=True, reconnect.starttime, and reconnect.endtime through the same setconfigvalue() endpoint to control when execution occurs. togglereconnect() at line 321 requires only Perms.STATUS — an even lower privilege.

4. Additional privilege escalation via config access

Beyond RCE, the same unrestricted config write allows SETTINGS users to: - Read proxy credentials (proxy.username/proxy.password) in plaintext via getconfig() - Redirect syslog to an attacker-controlled server (log.sysloghost/log.syslogport) - Disable SSL (webui.usessl=False), rebind to 0.0.0.0 (webui.host) - Modify SSL certificate/key paths to enable MITM

PoC

Step 1: Set reconnect script to an attacker-controlled executable

Via API: bash Authenticate and get session (as user with SETTINGS permission) curl -c cookies.txt -X POST 'http://target:8000/api/login' \ -d 'username=settingsuser&password=pass123'

Set reconnect script to a known executable on the system curl -b cookies.txt -X POST 'http://target:8000/api/setconfigvalue' \ -d 'category=reconnect&option=script&value=/tmp/exploit.sh&section=core'

Via Web UI: bash curl -b cookies.txt -X POST 'http://target:8000/json/saveconfig?category=core' \ -d 'reconnect|script=/tmp/exploit.sh&reconnect|enabled=True'

Step 2: Enable reconnect and set timing window

bash curl -b cookies.txt -X POST 'http://target:8000/api/setconfigvalue' \ -d 'category=reconnect&option=enabled&value=True&section=core'

curl -b cookies.txt -X POST 'http://target:8000/api/setconfigvalue' \ -d 'category=reconnect&option=starttime&value=00:00&section=core'

curl -b cookies.txt -X POST 'http://target:8000/api/setconfigvalue' \ -d 'category=reconnect&option=endtime&value=23:59&section=core'

Step 3: Script executes when thread manager calls tryreconnect()

The thread manager's run() method (called repeatedly by the core loop) invokes tryreconnect(), which calls subprocess.run(reconnectscript) at threadmanager.py:199.

Note on exploitation constraints: The file at the target path must exist (os.path.isfile() check) and be executable. With shell=False (subprocess.run default), no arguments are passed. If the attacker also has ADD permission (common for non-admin users), they can use pyLoad to download an archive containing an executable script, which may retain execute permissions after extraction.

Impact

- Remote Code Execution: A non-admin user with SETTINGS permission can execute arbitrary programs on the server as the pyLoad process user - Privilege escalation: The SETTINGS permission is described as "can access settings" — granting it is not expected to grant arbitrary code execution capability - Credential exposure: SETTINGS users can read proxy credentials, SSL key paths, and other sensitive config values via getconfig() - Network reconfiguration: SETTINGS users can disable SSL, change bind address, redirect logging, and modify other security-critical network settings

Recommended Fix

Add an allowlist or category-level restriction in setconfigvalue() that prevents non-admin users from modifying security-critical options:

python In setconfigvalue(), after the storagefolder check: ADMINONLYOPTIONS = { ("reconnect", "script"), ("webui", "host"), ("webui", "usessl"), ("webui", "sslcert"), ("webui", "sslkey"), ("log", "sysloghost"), ("log", "syslogport"), ("proxy", "username"), ("proxy", "password"), }

if section == "core" and (category, option) in ADMINONLYOPTIONS: # Require ADMIN role for security-critical settings if not self.pyload.api.userdata.get("role") == Role.ADMIN: raise PermissionError(f"Admin role required to modify {category}.{option}")

Additionally, consider validating the reconnect.script path against an allowlist of directories or requiring admin approval for script path changes.