CVE-2024-7589
📋 TL;DR
CVE-2024-7589 is a race condition vulnerability in OpenSSH's sshd on FreeBSD systems that allows unauthenticated remote attackers to potentially execute arbitrary code with root privileges. The vulnerability occurs when a signal handler calls non-async-signal-safe logging functions during client authentication timeout. This affects FreeBSD systems with OpenSSH integrated with blacklistd.
💻 Affected Systems
- OpenSSH on FreeBSD
📦 What is this software?
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
⚠️ Risk & Real-World Impact
Worst Case
Remote unauthenticated attacker gains full root access to the system, enabling complete system compromise, data theft, and lateral movement.
Likely Case
Successful exploitation leads to remote code execution as root, allowing attacker to install backdoors, steal credentials, and pivot to other systems.
If Mitigated
With proper network segmentation and access controls, impact is limited to the SSH server system only, though root compromise remains severe.
🎯 Exploit Status
Exploitation requires race condition timing and specific FreeBSD configuration. Similar to CVE-2024-6387 but in different code path.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: FreeBSD security patch FreeBSD-SA-24:08.openssh
Vendor Advisory: https://security.freebsd.org/advisories/FreeBSD-SA-24:08.openssh.asc
Restart Required: Yes
Instructions:
1. Update FreeBSD system using 'freebsd-update fetch' and 'freebsd-update install' 2. Restart sshd service 3. Verify patch is applied
🔧 Temporary Workarounds
Reduce LoginGraceTime
allShorten authentication timeout window to reduce attack surface
Edit /etc/ssh/sshd_config and set: LoginGraceTime 30
Restart sshd: service sshd restart
Disable blacklistd integration
FreeBSDRemove vulnerable code path by disabling blacklistd in sshd
Edit /etc/ssh/sshd_config and set: UseBlacklist no
Restart sshd: service sshd restart
🧯 If You Can't Patch
- Implement network segmentation to restrict SSH access to trusted sources only
- Deploy SSH bastion host with patched version and require jump-through access
🔍 How to Verify
Check if Vulnerable:
Check if running FreeBSD with OpenSSH using blacklistd: grep UseBlacklist /etc/ssh/sshd_configCheck Version:
freebsd-version -ku; ssh -VVerify Fix Applied:
Verify FreeBSD security patch is installed: freebsd-version -ku📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by timeout
- Unusual root-level process execution from sshd
Network Indicators:
- Multiple SSH connection attempts from single source with timing patterns
- Unexpected outbound connections from SSH server
SIEM Query:
source="sshd" AND ("authentication timeout" OR "LoginGraceTime") AND dest_user="root"