Analysis Summary

A new vulnerability in select versions of the OpenSSH secure networking suite, tracked as CVE-2024-6409, has been identified allowing for potential remote code execution (RCE).

This flaw affects versions 8.7p1 and 8.8p1 of OpenSSH and was shipped with Red Hat Enterprise Linux 9. It is characterized by a race condition in signal handling within the privsep child process which operates with reduced privileges compared to the parent server process, thereby lowering the immediate impact but still presenting significant risks.

The discovery of CVE-2024-6409 came during a review of a related vulnerability, CVE-2024-6387 (RegreSSHion) disclosed earlier by researchers. Both vulnerabilities involve a race condition triggered by the SIGALRM handler when a client fails to authenticate within the LoginGraceTime period (120 seconds by default). This condition invokes non-async-signal-safe functions leading to potential RCE. The main difference is that CVE-2024-6409 impacts the less-privileged privsep child process altering the dynamics of exploitability and impact.

Despite the lower privileges of the affected process, the risk remains substantial. A successful attack exploiting CVE-2024-6409 could allow an attacker to execute code within the context of an unprivileged user running the sshd server. This vulnerability mirrors CVE-2024-6387 in its mechanism emphasizing the need for comprehensive fixes and mitigations for both issues to prevent exploitation.

Notably, CVE-2024-6387 has already seen active exploitation in the wild with attacks primarily targeting servers in China. The initial attack vector has been traced to IP address 108.174.58.28, which hosts tools and scripts for automating the exploitation of vulnerable SSH servers. This active threat underscores the urgency of addressing both vulnerabilities to protect affected systems from potential breaches.

Impact

• Remote Code Execution
• Sensitive Data Theft

Indicators of Compromise

IP

• 108.174.58.28

Affected Vendors

Remediation

• Upgrade to the latest version of OpenSSH, available from the OpenSSH Website.
• Organizations must test their assets for the vulnerability mentioned above and apply the available security patch or mitigation steps as soon as possible.
• Implement multi-factor authentication to add an extra layer of security to login processes.
• Regularly monitor network activity for any unusual behavior, as this may indicate that a cyberattack is underway.
• Organizations must stay vigilant and follow best practices for cybersecurity to protect their systems and data from potential threats. This includes regularly updating software and implementing strong access controls and monitoring tools.
• Develop a comprehensive incident response plan to respond effectively in case of a security breach or data leakage.
• Maintain regular backups of critical data and systems to ensure data recovery in case of a security incident.
• Adhere to security best practices, including the principle of least privilege, and ensure that users and applications have only the necessary permissions.
• Establish a robust patch management process to ensure that security patches are evaluated, tested, and applied promptly.
• Conduct security audits and assessments to evaluate the overall security posture of your systems and networks.
• Implement network segmentation to contain and isolate potential threats to limit their impact on critical systems.