Source: cve@mitre.org
In Nagios XI 5.6.9, an authenticated user is able to execute arbitrary OS commands via shell metacharacters in the id parameter to schedulereport.php, in the context of the web-server user account.
Nagios XI 5.6.9 is vulnerable to remote command execution (RCE), allowing an authenticated attacker to execute arbitrary operating system commands. This vulnerability, exploitable through the schedulereport.php script, could lead to complete system compromise and data exfiltration. Successful exploitation grants the attacker control under the web server's user account.
Step 1: Authentication: The attacker must first authenticate to the Nagios XI web interface. This typically requires valid credentials.
Step 2: Payload Crafting: The attacker crafts a malicious payload containing shell metacharacters (e.g., ;, |, &, &&) designed to execute arbitrary commands. This payload is designed to be injected into the id parameter of the schedulereport.php script.
Step 3: Payload Delivery: The attacker sends a crafted HTTP request to schedulereport.php, including the malicious payload in the id parameter.
Step 4: Command Execution: The schedulereport.php script processes the request. Due to the lack of input validation, the injected shell metacharacters are interpreted by the operating system's shell.
Step 5: Command Execution: The injected commands are executed with the privileges of the web server user (e.g., www-data, apache).
Step 6: Result: The attacker's commands are executed, potentially allowing them to read files, execute further commands, or gain control of the system.
The vulnerability stems from insufficient input validation in the schedulereport.php script within Nagios XI 5.6.9. Specifically, the script fails to properly sanitize the id parameter before passing it to a shell command. This allows an authenticated user to inject shell metacharacters into the id parameter, which are then executed by the operating system. The root cause is a lack of proper input sanitization and output encoding, leading to a command injection vulnerability. The script likely uses a function like exec(), system(), or shell_exec() to execute the command, without properly escaping or validating the user-supplied input. This allows an attacker to inject arbitrary commands, potentially leading to privilege escalation if the web server user has elevated permissions.
While no specific APT groups are definitively linked, the ease of exploitation makes this a target for a wide range of attackers, including those seeking initial access. This vulnerability could be leveraged by ransomware groups for initial access and lateral movement. CISA KEV status is likely, given the severity and ease of exploitation.
Monitor web server access logs (e.g., Apache, Nginx) for suspicious POST requests to schedulereport.php with unusual id parameter values containing shell metacharacters.
Analyze network traffic for unusual HTTP POST requests to schedulereport.php with payloads that include shell metacharacters.
Monitor file system activity for unexpected file creations or modifications, especially those related to the web server user.
Implement file integrity monitoring to detect changes to critical system files.
Use intrusion detection/prevention systems (IDS/IPS) with signatures for this specific vulnerability or generic command injection attempts.
Review system logs for evidence of command execution by the web server user, especially commands that are not part of normal operation.
Upgrade to a patched version of Nagios XI that addresses the vulnerability. Consult the Nagios XI documentation for the latest version and upgrade instructions.
Implement input validation and output encoding in schedulereport.php to properly sanitize the id parameter. This includes escaping special characters and using a whitelist approach to validate the input.
Restrict the permissions of the web server user to the minimum necessary for its operation. This limits the potential damage if the system is compromised.
Implement a web application firewall (WAF) to filter malicious requests and block attempts to exploit the vulnerability.
Regularly scan the system for vulnerabilities using a vulnerability scanner.
Implement multi-factor authentication (MFA) for all user accounts to prevent unauthorized access.
Monitor system logs and network traffic for suspicious activity.