Openssh: regresshion - race condition in ssh allows rce/dos

Primary CVSS: v3.1 8.1 HIGH from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Problem Types: CWE-364 | CWE-362 | CWE-364 Signal Handler Race Condition

Discovery Credit

CNA: Red Hat would like to thank Qualys Threat Research Unit (TRU) (Qualys) for reporting this issue. (en)

Workarounds

CNA: The below process can protect against a Remote Code Execution attack by disabling the LoginGraceTime parameter on Red Hat Enterprise Linux 9. However, the sshd server is still vulnerable to a Denial of Service if an attacker exhausts all the connections. 1) As root user, open the /etc/ssh/sshd_config 2) Add or edit the parameter configuration: ~~~ LoginGraceTime 0 ~~~ 3) Save and close the file 4) Restart the sshd daemon: ~~~ systemctl restart sshd.service ~~~ Setting LoginGraceTime to 0 disables the SSHD server's ability to drop connections if authentication is not completed within the specified timeout. If this mitigation is implemented, it is highly recommended to use a tool like 'fail2ban' alongside a firewall to monitor log files and manage connections appropriately. If any of the mitigations mentioned above is used, please note that the removal of LoginGraceTime parameter from sshd_config is not automatic when the updated package is installed.