Attack Chain

1. Attacker authenticates to the VA MAX 8.3.4 web interface using valid credentials.
2. Attacker crafts a malicious POST request targeting the changeip.php endpoint.
3. The POST request includes the mtu_eth0 parameter containing shell metacharacters and the desired command for execution.
4. The changeip.php script processes the mtu_eth0 parameter without proper sanitization or validation.
5. The injected shell metacharacters are interpreted by the system, leading to command execution.
6. The attacker-supplied command is executed with the privileges of the apache user.
7. The attacker gains control of the system, potentially installing malware, exfiltrating data, or performing other malicious activities.

Impact

Successful exploitation of CVE-2019-25671 allows an attacker to execute arbitrary commands on the affected VA MAX 8.3.4 system. This can lead to complete system compromise, data theft, and disruption of services. If VA MAX manages critical infrastructure, this vulnerability could have significant real-world consequences. Given the publicly available exploit code, the risk of widespread exploitation is high.

Recommendation

• Monitor web server logs for POST requests to changeip.php containing shell metacharacters in the mtu_eth0 parameter using the provided Sigma rule.
• Apply appropriate input validation and sanitization to the mtu_eth0 parameter within the changeip.php script.
• Consider upgrading to a patched version of VA MAX that addresses CVE-2019-25671.
• Implement network segmentation to limit the potential impact of a compromised VA MAX system.
• Review and enforce strong password policies to prevent unauthorized access to the VA MAX web interface.
• Monitor for suspicious processes spawned by the apache user, which could indicate successful exploitation of the RCE vulnerability using the Sigma rule Detect Suspicious Processes Spawned by Apache.