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 glibc-based Linux systems. Immediate patching is essential to prevent severe compromise.
What is OpenSSH regreSSHion – Unauthenticated RCE?
This vulnerability stems from a signal handler race condition within the OpenSSH server (sshd) process. Specifically, it affects OpenSSH versions 8.5p1 through 9.7p1 running on glibc-based Linux distributions. An attacker can exploit this race condition to execute arbitrary code with root privileges on the target system without any prior authentication.
Impact and Risks for your Infrastructure
The impact of CVE-2024-6387 is severe, leading to a complete root compromise of affected SSH servers. Attackers can execute arbitrary code, gaining full control over the compromised system. This can result in data exfiltration, service disruption, and further network penetration, posing a significant risk to critical infrastructure.
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 version (sshd -V) and ensuring it reflects the patched version. Restart the sshd service to apply the changes and confirm the vulnerability is no longer present.
- 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).