What is CVE-2024-6387?

A signal handler race condition in OpenSSH's server (sshd) allows unauthenticated remote code execution as root on glibc-based Linux systems. Affects OpenSSH 8.5p1–9.7p1.

How do I fix CVE-2024-6387?

Upgrade OpenSSH to 9.8p1 or later immediately. Restrict SSH access via firewall: allow only trusted IPs on port 22. Enable fail2ban or equivalent rate-limiting to slow exploitation attempts. Set LoginGraceTime 0 in sshd_config as a temporary workaround (disables grace period). Audit SSH server logs for exploitation attempts (look for connection floods). Consider moving SSH to a non-standard port or VPN-only access (Tailscale, WireGuard).

Which versions are affected by CVE-2024-6387?

Affected: OpenSSH 8.5p1 – 9.7p1 (glibc Linux). Fixed in: OpenSSH 9.8p1+.

criticalCVSS 8.1/10·Published: 2024-07-01·OpenSSH

How to fix CVE-2024-6387 – Step-by-Step Guide

CVE-2024-6387, dubbed "regreSSHion," is a critical vulnerability affecting OpenSSH servers. This flaw enables unauthenticated remote code execution (RCE) as root on vulnerable glibc-based Linux systems. Immediate action is required to prevent severe security breaches.

CVE ID

CVE-2024-6387

Severity

CRITICAL

CVSS Score

8.1/10

Affected

OpenSSH

What is OpenSSH regreSSHion – Unauthenticated RCE?

This vulnerability stems from a signal handler race condition within the OpenSSH server (sshd) process. Exploiting this race condition allows an attacker to bypass authentication mechanisms entirely. It specifically impacts OpenSSH versions 8.5p1 through 9.7p1 running on systems utilizing glibc.

Affected Versions

OpenSSH 8.5p1 – 9.7p1 (glibc Linux)

Fixed In

OpenSSH 9.8p1+

Official References

Impact and Risks for your Infrastructure

Successful exploitation of CVE-2024-6387 leads to a full root compromise of the affected SSH server. An attacker can execute arbitrary code with root privileges, gaining complete and unauthenticated control over the underlying system. This poses an extreme risk to data integrity and system availability.

opensshrcecriticallinux2024

Step-by-Step Mitigation Guide

To remediate CVE-2024-6387, administrators must upgrade their OpenSSH installation to version 9.8p1 or newer immediately. Verify the fix by checking your OpenSSH version (e.g., `ssh -V`) to confirm it is 9.8p1+. Ensure all affected systems are updated promptly.

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).

Frequently Asked Questions

What is the CVSS score for CVE-2024-6387?▼

CVE-2024-6387 has a CVSS score of 8.1/10 (critical severity). This reflects the most severe potential impact, requiring immediate remediation.

Which versions of OpenSSH are affected?▼

Affected: OpenSSH 8.5p1 – 9.7p1 (glibc Linux). The vulnerability was fixed in: OpenSSH 9.8p1+.

How long does it take to fix CVE-2024-6387?▼

For most teams: 15–60 minutes to apply the patch, plus 15 minutes of post-patch verification. Complex multi-service environments may require 2–4 hours including staging validation.

Is CVE-2024-6387 being actively exploited?▼

Check the NVD entry and CISA KEV catalog for exploitation status. As a critical-severity vulnerability, treat it as a priority remediation regardless of known exploitation status.

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This CVE fix guide is based on publicly available security advisories (NVD, vendor bulletins). Always test changes in a staging environment before applying to production. Verify against the official vendor advisory for the most up-to-date guidance.