Source: cve@mitre.org
Sendmail WIZ command enabled, allowing root access.
Critical vulnerability in Sendmail versions prior to 8.9.3 allowed attackers to gain root access by exploiting the enabled WIZ command. This flaw permitted unauthorized execution of commands with elevated privileges, leading to complete system compromise and potential data breaches. Immediate patching and configuration review are crucial to mitigate this severe risk.
Step 1: Target Identification: The attacker identifies a Sendmail server with the WIZ command enabled. This can be achieved through port scanning (port 25) and banner grabbing.
Step 2: WIZ Command Activation: The attacker connects to the Sendmail server via SMTP and issues the WIZ command. This command is typically used for debugging and allows privileged access.
Step 3: Payload Injection: The attacker crafts a malicious command or series of commands to be executed via the WIZ command. This payload is injected as part of the WIZ command's arguments.
Step 4: Command Execution: The Sendmail daemon, due to the lack of proper input validation and authorization, executes the attacker's injected command with root privileges.
Step 5: System Compromise: The attacker's command(s) are executed, allowing them to gain root access, install backdoors, steal data, or otherwise compromise the system.
The vulnerability stems from the Sendmail daemon's handling of the WIZ command, a debugging feature intended for internal use. When enabled, this command bypasses normal access controls and allows the execution of arbitrary commands with root privileges. The root cause is a lack of proper input validation and authorization checks for the WIZ command. Specifically, the Sendmail daemon trusts the input provided via the WIZ command, failing to sanitize or validate it before execution. This allows an attacker to inject malicious commands that are then executed with elevated privileges. The absence of proper authentication and authorization mechanisms for the WIZ command is the fundamental flaw.
This vulnerability is a classic example of a privilege escalation attack. While specific APT groups are not directly linked to this specific CVE, any threat actor with the knowledge and resources to exploit vulnerabilities would likely target vulnerable Sendmail installations. This vulnerability is not listed on the CISA KEV list, but its potential for complete system compromise makes it a high-priority target for attackers.
Monitor SMTP traffic for the WIZ command. Unusual or unexpected use of this command should be investigated immediately.
Review Sendmail logs for suspicious activity, including attempts to execute commands with elevated privileges.
Implement intrusion detection systems (IDS) and intrusion prevention systems (IPS) with signatures that detect the WIZ command and known exploitation attempts.
Analyze system logs for any unexpected changes to system files or user accounts, which could indicate a successful compromise.
Use file integrity monitoring tools to detect unauthorized modifications to critical system files.
Patch Immediately: Upgrade Sendmail to a version that addresses the vulnerability (8.9.3 or later).
Disable the WIZ Command: If upgrading is not immediately possible, disable the WIZ command in the Sendmail configuration. This is the most critical immediate step.
Implement Strong Authentication: Enforce strong authentication mechanisms for all Sendmail access.
Least Privilege Principle: Ensure that Sendmail runs with the minimum necessary privileges.
Regular Security Audits: Conduct regular security audits and penetration testing to identify and address vulnerabilities.
Network Segmentation: Isolate the Sendmail server from other critical systems to limit the impact of a compromise.