CVE-2021-40119
📋 TL;DR
This vulnerability allows unauthenticated remote attackers to gain root access to Cisco Policy Suite systems by exploiting reused static SSH keys across installations. Attackers can extract keys from compromised systems to access other vulnerable installations. All Cisco Policy Suite deployments using affected versions are at risk.
💻 Affected Systems
- Cisco Policy Suite
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with root-level access, enabling data theft, service disruption, and lateral movement to other systems.
Likely Case
Unauthorized root access leading to data exfiltration, configuration changes, and installation of persistent backdoors.
If Mitigated
Limited impact if SSH access is restricted to management networks and proper network segmentation is in place.
🎯 Exploit Status
Exploitation requires obtaining static SSH keys from any compromised system, which can then be used against all other vulnerable installations.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 21.1.0 and later
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-cps-static-key-JmS92hNv
Restart Required: Yes
Instructions:
1. Upgrade to Cisco Policy Suite version 21.1.0 or later. 2. Follow Cisco's upgrade documentation for your specific deployment. 3. Restart affected services after upgrade.
🔧 Temporary Workarounds
Restrict SSH Access
linuxLimit SSH access to trusted management networks using firewall rules.
iptables -A INPUT -p tcp --dport 22 -s TRUSTED_NETWORK -j ACCEPT
iptables -A INPUT -p tcp --dport 22 -j DROP
Replace Static SSH Keys
linuxGenerate and deploy unique SSH keys for each installation.
ssh-keygen -t rsa -b 4096 -f /etc/ssh/ssh_host_rsa_key
systemctl restart sshd
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Cisco Policy Suite from untrusted networks.
- Deploy host-based intrusion detection and monitor for unauthorized SSH access attempts.
🔍 How to Verify
Check if Vulnerable:
Check Cisco Policy Suite version: if below 21.1.0, system is vulnerable. Also verify if SSH keys match known static keys from other installations.Check Version:
cps version or check version in web interfaceVerify Fix Applied:
Confirm version is 21.1.0 or later and verify SSH keys are unique by comparing with other systems.📡 Detection & Monitoring
Log Indicators:
- Failed SSH authentication attempts from unexpected sources
- Successful root SSH logins from unknown IPs
- SSH key mismatch warnings
Network Indicators:
- SSH connections from unusual locations or IP ranges
- Multiple SSH authentication attempts
SIEM Query:
source="auth.log" AND "sshd" AND ("Accepted publickey" OR "Failed publickey") AND (user="root" OR user="admin")