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OpenSSH Vulnerability - regreSSHion: Remote Code Execution (CVE-2024-6387)

Advisory

Advisory
02 JULY 2024

 

Background

A critical vulnerability known as regreSSHion (CVE-2024-6387), has been discovered in OpenSSH, a widely used open-source implementation for secure network communication. This vulnerability allows an unauthenticated attacker to remotely execute arbitrary code with root privileges on Linux systems running OpenSSH servers.

The regreSSHion vulnerability is a race condition in OpenSSH's server (sshd) that occurs in the signal handler. This flaw can be exploited by an attacker to execute code remotely without authentication on Linux systems based on the glibc library. It is important to note that Windows and macOS systems are not currently known to be affected.

 

Impact

Successful exploitation of this vulnerability can lead to the compromise of the target system, allowing the attacker to gain full control and bypass security measures. This can result in unauthorized access, data theft, and the ability to maintain persistent access to the compromised system.

 

Affected Products

The following versions of OpenSSH are impacted by this vulnerability:

  • OpenSSH versions earlier than 4.4p1
  • OpenSSH versions between 8.5p1 and 9.8p1 (excluding)

The vulnerability is exploitable on glibc-based Linux distributions (e.g., Debian-based).

 

Recommendations

To mitigate the regreSSHion vulnerability, it is recommended to take the following actions:

  • Update OpenSSH: Install the latest patched version of OpenSSH that addresses the regreSSHion vulnerability. Ensure that all affected systems are updated promptly.
  • Restrict External SSH Access: As a temporary measure, limit access to SSH from external IP addresses. This can help reduce the risk of exploitation until the OpenSSH update is applied.
  • Monitor for Exploitation Attempts: Keep an eye on network and system logs for any suspicious activity or attempts to exploit this vulnerability. Implement appropriate monitoring and detection mechanisms.
  • Follow Best Practices: Adhere to security best practices, such as strong passwords, regular system patching, and network segmentation, to minimize the impact of potential attacks.

It is crucial to apply the necessary updates and implement mitigation measures promptly to protect systems from the regreSSHion vulnerability. Regularly monitoring official sources for security updates and advisories is recommended to stay informed about potential threats and vulnerabilities.

 

References