CVE-2025-20239
📋 TL;DR
An unauthenticated remote attacker can send crafted IKEv2 packets to trigger a memory leak in affected Cisco devices, causing denial of service. Cisco IOS/IOS XE devices may reload unexpectedly, while ASA/FTD devices may experience memory exhaustion and VPN session failures. This affects Cisco devices running vulnerable IKEv2 implementations.
💻 Affected Systems
- Cisco IOS Software
- Cisco IOS XE Software
- Cisco Secure Firewall ASA Software
- Cisco Secure Firewall FTD Software
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Complete device outage requiring manual reboot, disrupting all network services and VPN connectivity
Likely Case
Partial memory exhaustion leading to VPN session failures and system instability
If Mitigated
Minimal impact if IKEv2 is disabled or devices are behind proper network controls
🎯 Exploit Status
Exploitation requires network access to IKEv2 ports (typically UDP 500/4500)
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Cisco advisory for specific fixed versions per product
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-ftd-ios-dos-DOESHWHy
Restart Required: Yes
Instructions:
1. Review Cisco advisory for affected versions
2. Download appropriate fixed software version
3. Schedule maintenance window
4. Apply patch following Cisco upgrade procedures
5. Reboot device as required
🔧 Temporary Workarounds
Disable IKEv2
allDisable IKEv2 feature if not required, use IKEv1 instead
crypto ikev2 disable
Restrict IKEv2 Access
allImplement ACLs to restrict IKEv2 traffic to trusted sources only
access-list IKEV2-ACL permit udp trusted-source any eq 500
access-list IKEV2-ACL permit udp trusted-source any eq 4500
access-list IKEV2-ACL deny udp any any eq 500
access-list IKEV2-ACL deny udp any any eq 4500
🧯 If You Can't Patch
- Implement strict network ACLs to block IKEv2 traffic from untrusted sources
- Monitor device memory usage and IKEv2 session logs for anomalies
🔍 How to Verify
Check if Vulnerable:
Check device version against Cisco advisory; verify IKEv2 is enabled with 'show crypto ikev2 sa' or similar commandsCheck Version:
show version | include VersionVerify Fix Applied:
Verify running version matches fixed version from advisory; confirm IKEv2 functionality remains operational📡 Detection & Monitoring
Log Indicators:
- Memory allocation failures
- IKEv2 session establishment failures
- Device reload events without clear cause
- High memory utilization alerts
Network Indicators:
- Unusual IKEv2 traffic patterns
- IKEv2 packets from unexpected sources
- VPN connectivity issues
SIEM Query:
source="cisco-asa" OR source="cisco-ios" ("IKEv2" AND ("memory" OR "reload" OR "failure"))