CVE-2022-20742
📋 TL;DR
This vulnerability allows an unauthenticated remote attacker in a man-in-the-middle position to decrypt, read, modify, and re-encrypt data transmitted across affected IPsec IKEv2 VPN tunnels. It affects Cisco ASA and Firepower Threat Defense (FTD) software due to improper Galois/Counter Mode (GCM) cipher implementation. Organizations using these products for VPN connectivity are at risk.
💻 Affected Systems
- Cisco Adaptive Security Appliance (ASA) Software
- Cisco Firepower Threat Defense (FTD) Software
📦 What is this software?
Adaptive Security Appliance Software by Cisco
View all CVEs affecting Adaptive Security Appliance Software →
Adaptive Security Appliance Software by Cisco
View all CVEs affecting Adaptive Security Appliance Software →
Adaptive Security Appliance Software by Cisco
View all CVEs affecting Adaptive Security Appliance Software →
Adaptive Security Appliance Software by Cisco
View all CVEs affecting Adaptive Security Appliance Software →
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of VPN tunnel confidentiality and integrity, allowing attackers to read sensitive data, inject malicious content, or impersonate legitimate endpoints.
Likely Case
Selective decryption and manipulation of VPN traffic, potentially exposing credentials, sensitive communications, or enabling further network penetration.
If Mitigated
Limited impact if VPN tunnels are monitored and segmented, though cryptographic weaknesses remain exploitable by determined attackers.
🎯 Exploit Status
Requires man-in-the-middle position and ability to intercept sufficient encrypted messages. Cryptanalytic techniques needed to break encryption.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Multiple fixed versions available - see Cisco advisory for specific releases
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-ipsec-mitm-CKnLr4
Restart Required: Yes
Instructions:
1. Review Cisco advisory for affected versions. 2. Upgrade to fixed software releases. 3. Restart affected devices after patching. 4. Verify VPN functionality post-upgrade.
🔧 Temporary Workarounds
Disable GCM Ciphers
allRemove Galois/Counter Mode (GCM) ciphers from IPsec IKEv2 VPN configurations to mitigate the vulnerability
crypto ikev2 policy 1
no encryption aes-gcm-256
no encryption aes-gcm-192
no encryption aes-gcm-128
🧯 If You Can't Patch
- Implement workaround to disable GCM ciphers in IPsec IKEv2 VPN configurations
- Monitor VPN traffic for anomalies and implement additional network segmentation for VPN-connected resources
🔍 How to Verify
Check if Vulnerable:
Check if device runs affected ASA/FTD software version and has IPsec IKEv2 VPN with GCM ciphers enabledCheck Version:
show versionVerify Fix Applied:
Verify software version is updated to fixed release and GCM ciphers are disabled or device is patched📡 Detection & Monitoring
Log Indicators:
- Unusual VPN connection patterns
- Failed VPN authentication attempts
- VPN tunnel renegotiation anomalies
Network Indicators:
- Unusual traffic patterns in VPN tunnels
- Man-in-the-middle attack signatures
- VPN protocol anomalies
SIEM Query:
source="cisco_asa" OR source="cisco_ftd" AND (event_type="vpn" OR protocol="ipsec") AND (status="failed" OR anomaly_score>7)