CVE-2022-20756
📋 TL;DR
This vulnerability in Cisco ISE's RADIUS feature allows an unauthenticated remote attacker to send crafted RADIUS requests, causing the system to stop processing RADIUS packets and leading to denial of service for authentication and authorization. It affects organizations using Cisco ISE as a RADIUS server, potentially disrupting network access for legitimate users until a manual restart is performed.
💻 Affected Systems
- Cisco Identity Services Engine (ISE)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete disruption of RADIUS-based authentication across the network, causing widespread access denials and operational downtime until manual intervention.
Likely Case
Intermittent authentication timeouts and access failures for users, requiring IT staff to restart affected Policy Service Nodes to restore service.
If Mitigated
Limited impact if network segmentation or rate-limiting blocks malicious traffic, but risk remains if vulnerable systems are exposed.
🎯 Exploit Status
Exploitation involves sending specific RADIUS requests, which may be straightforward for attackers with network access to the target.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Cisco ISE version 3.1 Patch 1 or later, as per vendor advisory.
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ise-dos-JLh9TxBp
Restart Required: Yes
Instructions:
1. Review the Cisco advisory for exact patch details. 2. Download and apply the patch from Cisco's support site. 3. Restart the affected Policy Service Nodes to implement the fix.
🔧 Temporary Workarounds
Network Segmentation and Access Control
allRestrict access to the RADIUS service by implementing firewall rules or network segmentation to block untrusted sources from sending RADIUS requests.
🧯 If You Can't Patch
- Implement strict network access controls to limit RADIUS traffic to trusted sources only.
- Monitor logs for unusual RADIUS request patterns and prepare for manual restart procedures if exploitation occurs.
🔍 How to Verify
Check if Vulnerable:
Check the Cisco ISE version via the admin interface or CLI; if running version 3.0, 3.1, or earlier without the patch, the system is vulnerable.Check Version:
show version (in Cisco ISE CLI) or check via the ISE admin GUI under Administration > System > About.Verify Fix Applied:
After patching, confirm the version is updated to 3.1 Patch 1 or later and test RADIUS functionality to ensure no service interruptions.📡 Detection & Monitoring
Log Indicators:
- Unusual RADIUS authentication failures or timeouts in ISE logs
- Log entries indicating Policy Service Node restarts due to crashes.
Network Indicators:
- Spikes in RADIUS request traffic from unknown sources
- Failed authentication attempts with malformed packets.
SIEM Query:
Example: search for 'RADIUS' AND ('failure' OR 'timeout') in Cisco ISE logs within a short time window.