A flaw in libssh allows a remote attacker, by controlling client configuration files or known_hosts files, to craft hostnames that trigger inefficient regular expression backtracking within the match_pattern() function. This backtracking can consume excessive processor time and memory, ultimately causing the client to time out or become unresponsive, which manifests as a denial of service for anyone using that client.

The vulnerability impacts Red Hat products including Red Hat Enterprise Linux 10, 6, 7, 8, and 9, Red Hat Hardened Images, and Red Hat OpenShift Container Platform 4, as well as all distributions employing libssh 0.12.0 or 0.11.4. The affected components are present in the listed RHEL releases and OpenShift 4, and the issue originates from the libssh library used by these platforms.

The CVSS score of 5.5 indicates a medium severity, and the EPSS score of less than 1% shows a very low probability of current exploitation. The vulnerability is not listed in the CISA KEV catalog. Exploitation requires an attacker to supply crafted configuration or known_hosts entries, which can be done remotely if the attacker can influence those files. Once exploited, the attack can lead to client-side resource exhaustion and denial of service without compromising confidentiality or integrity.