Описание
LibreNMS Vulnerable to Remote Code Execution by Signal Alert Transportation module
Summary
A vulnerability has been identified that allows an authenticated administrator to execute arbitrary code on the host server. By adding an alert transport entry, an attacker with administrative privileges can execute malicious commands.
Details
The vulnerability is caused by an unsafe exec call in deliverAlert function of LibreNMS/Alert/Transport/Signal.php. Escapes for the path of signal-cli and the Recipient field are insufficient to prevent command-line injection.
The composer_wrapper.php under scripts is also vulnerable to command injection (unsafe exec calls) by passing the injected command as an argument, and it is accepting arguments passed by deliverAlert.
By chaining these unsafe exec calls, malicious admin user can execute any executables in the server's filesystem.
PoC
- Under Dashboard -> Alert -> Alert Transports
- Create a new Alert Transport entry.
a. Select
SignalasTransport type. b. Put../scripts/composer_wrapper.phpintoPath. c. Put the command to execute underRecipientwith;at the start and the end of string.
- . Click
Save Transport, and after the popup closed, clickTest Transportbutton underActionof the created Alert Transport entry.
- The command is executed.
Impact
This vulnerability allows a malicious actor to achieve Remote Code Execution (RCE), potentially leading to complete system compromise, data exfiltration, or lateral movement within the network.
Remediation Advice
Escape user inputs, and avoid passing them directly into exec function. (scripts/composer_wrapper.php)
Avoid setting executable paths directly in web interface. Instead, use a config value, and only allow setting executable paths by command line interface. (LibreNMS/Alert/Transport/Signal.php)
Пакеты
librenms/librenms
>= 21.6.0, < 26.5.0
26.5.0
Связанные уязвимости
LibreNMS is a network monitoring system. In versions from 21.6.0 up to 26.5.0, the Signal alert transport is vulnerable to command injection because the signal-cli path and the Recipient field of an alert transport entry are insufficiently escaped before being passed to an exec call. An authenticated administrator can craft a transport entry whose Recipient contains shell metacharacters and whose path points to the bundled composer_wrapper.php script, which itself passes attacker-controlled input to further unsafe exec calls. By chaining these calls, the administrator can execute arbitrary operating-system commands on the LibreNMS host. This issue is fixed in version 26.5.0.