Security researchers have identified a new vulnerability in OpenSSH, designated CVE-2024-6409, which poses a risk of remote code execution (RCE). This flaw, affecting OpenSSH versions 8.7 and 8.8, is caused by a race condition in the signal handling within the privilege separation (privsep) child process. The vulnerability allows for potential exploitation due to improper handling in the grace_alarm_handler() function, which calls cleanup_exit() in an unsafe context.
The issue was disclosed on July 8, 2024, following an analysis by Qualys and further review by security experts. Unlike a prior vulnerability, CVE-2024-6387, CVE-2024-6409 triggers RCE in the privsep child process, which operates with fewer privileges compared to the parent server process. Although this limits the immediate impact, the risk of remote code execution remains significant.
Mitigation steps include applying patches released by vendors such as Rocky Linux, adjusting configurations like setting LoginGraceTime to 0, and enhancing monitoring for unusual activity, especially around SSH daemon signal handling and authentication attempts. Despite the reduced privileges of the privsep child process, the vulnerability still represents a serious security threat.
The discovery of CVE-2024-6409 highlights the ongoing challenges in maintaining secure software environments. Organizations are urged to promptly update their systems, review their security configurations, and stay informed about vulnerabilities and available patches to protect against potential exploits.
