New OpenSSH Vulnerability Poses Remote Code Execution Risk
Recent security assessments have revealed that certain versions of the OpenSSH secure networking suite are vulnerable to a critical new exploit capable of enabling remote code execution (RCE). This vulnerability, designated as CVE-2024-6409, has an assigned CVSS score of 7.0, indicating a high severity level. Distinguishable from the previously disclosed CVE-2024-6387, known colloquially as RegreSSHion, CVE-2024-6409 arises from a race condition within the signal handling mechanism of the privsep child process. Notably, it affects only OpenSSH versions 8.7p1 and 8.8p1, specifically those distributed with Red Hat Enterprise Linux 9.
Alexander Peslyak, a security researcher widely recognized by his alias Solar Designer, discovered this vulnerability during an evaluation of CVE-2024-6387, which was reported earlier this month. Peslyak’s findings point out that while the potential impact of CVE-2024-6409 is less immediate due to its operation within a child process running with reduced privileges, it still represents a significant threat. The distinction in exploitability between these vulnerabilities may vary based on specific attack scenarios, which could make one exploit more appealing than the other to potential attackers.
The vulnerability manifests during a signal handler race condition, where an OpenSSH daemon process calls the SIGALRM handler asynchronously if a client fails to authenticate within the LoginGraceTime threshold, typically set to 120 seconds. This condition not only opens a window for exploitation but also leads to potential conflicts within the cleanup_exit() function in the unprivileged child of the SSHD server, echoing issues previously identified in CVE-2024-6387.
Should attackers successfully exploit this vulnerability, they may gain the capability to execute arbitrary code within the context of a non-privileged user running the sshd server, leading to broader system compromises. An active exploit for the related CVE-2024-6387 has already been detected, with reports indicating that unidentified threat actors are actively targeting systems primarily located in China.
The initial attack vectors for these incidents have been traced back to an IP address that reportedly served as a host for a directory listing of exploit tools and scripts, designed to automate the compromise of vulnerable SSH servers. As cybersecurity professionals look to mitigate these types of risks, references to the MITRE ATT&CK framework could shed light on likely adversary tactics that might include techniques for initial access, persistence, and privilege escalation.
As organizations strive to fortify their defenses against potential attacks linked to these vulnerabilities, it is imperative for system administrators to carefully monitor their OpenSSH implementations and apply pertinent patches as soon as they become available. Continuous vigilance against newly emerging threats remains crucial in today’s evolving threat landscape.
For additional updates on cybersecurity measures and vulnerabilities, professionals are encouraged to stay informed through reliable news sources and engage with the community on platforms such as Twitter and LinkedIn.
