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 root access without authentication on vulnerable glibc-based Linux systems. Immediate patching is crucial to prevent severe compromise.
What is OpenSSH regreSSHion – Unauthenticated RCE?
This vulnerability stems from a signal handler race condition in OpenSSH's sshd. An unauthenticated attacker can exploit a timing window to trigger arbitrary code execution as root. This bypasses authentication, leading to full system compromise on glibc-based Linux systems running affected OpenSSH versions.
Impact and Risks for your Infrastructure
The impact of CVE-2024-6387 is severe, leading to full root compromise of affected SSH servers. Attackers can execute arbitrary code, gaining complete control over the compromised system. This can result in data exfiltration, service disruption, and further network penetration.
Step-by-Step Mitigation Guide
To mitigate CVE-2024-6387, update your OpenSSH server to version 9.8p1 or higher immediately. Verify the update by checking `sshd -V` or your package manager's installed version. After patching, restart the sshd service to ensure the fix is active and consider a system reboot.
- 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).