How to fix CVE-2024-6387 – Step-by-Step Guide
CVE-2024-6387, dubbed "regreSSHion," is a critical unauthenticated Remote Code Execution (RCE) vulnerability affecting OpenSSH servers. This flaw allows attackers to gain full root control over vulnerable systems. Immediate patching is essential to prevent severe security breaches.
What is OpenSSH regreSSHion – Unauthenticated RCE?
This vulnerability stems from a signal handler race condition within OpenSSH's server daemon, sshd. On glibc-based Linux systems, an attacker can exploit this race condition without authentication. This leads to the execution of arbitrary code with root privileges, bypassing all security measures.
Impact and Risks for your Infrastructure
The primary impact is a complete root compromise of the affected SSH server. Attackers can execute arbitrary code, gaining full control over the system and its data. This can lead to data exfiltration, service disruption, and further network penetration.
Step-by-Step Mitigation Guide
To mitigate CVE-2024-6387, administrators must immediately upgrade OpenSSH to version 9.8p1 or newer. Verify the upgrade by checking the sshd -V output to confirm the installed version is 9.8p1+. Ensure all affected glibc-based Linux systems are patched.
- 1Upgrade OpenSSH to 9.8p1 or later immediately.
- 2Restrict SSH access via firewall: allow only trusted IPs on port 22.
- 3Enable fail2ban or equivalent rate-limiting to slow exploitation attempts.
- 4Set LoginGraceTime 0 in sshd_config as a temporary workaround (disables grace period).
- 5Audit SSH server logs for exploitation attempts (look for connection floods).
- 6Consider moving SSH to a non-standard port or VPN-only access (Tailscale, WireGuard).