CVE-2021-1594
📋 TL;DR
This vulnerability allows an unauthenticated remote attacker to execute arbitrary commands with root privileges on Cisco Identity Services Engine (ISE) by exploiting insufficient input validation in the REST API. Attackers need to decrypt HTTPS traffic between ISE personas on separate nodes to exploit it. Organizations running vulnerable Cisco ISE versions are affected.
💻 Affected Systems
- Cisco Identity Services Engine (ISE)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with root-level command execution, allowing attacker to steal sensitive data, deploy malware, or disrupt ISE operations.
Likely Case
Privilege escalation leading to unauthorized access to network authentication and policy systems, potentially compromising the entire identity management infrastructure.
If Mitigated
Limited impact if proper network segmentation, encryption, and monitoring prevent man-in-the-middle attacks between ISE nodes.
🎯 Exploit Status
Exploitation requires man-in-the-middle position to decrypt HTTPS traffic between ISE nodes, which adds complexity but is feasible in certain network configurations.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 3.1P1
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ise-priv-esc-UwqPrBM3
Restart Required: Yes
Instructions:
1. Download Cisco ISE 3.1P1 from Cisco Software Center. 2. Backup current configuration. 3. Apply patch following Cisco ISE upgrade procedures. 4. Restart ISE services as required.
🔧 Temporary Workarounds
Network Segmentation
allIsolate ISE nodes in protected network segments to prevent man-in-the-middle attacks
Enhanced TLS Monitoring
allImplement certificate pinning or enhanced TLS inspection between ISE nodes
🧯 If You Can't Patch
- Implement strict network access controls between ISE nodes to prevent traffic interception
- Deploy network monitoring and intrusion detection systems to detect man-in-the-middle attempts
🔍 How to Verify
Check if Vulnerable:
Check ISE version via admin GUI or CLI: show versionCheck Version:
show versionVerify Fix Applied:
Verify version is 3.1P1 or later and check for successful patch installation logs📡 Detection & Monitoring
Log Indicators:
- Unusual REST API requests
- Failed authentication attempts to API endpoints
- Unexpected process execution
Network Indicators:
- Unusual traffic patterns between ISE nodes
- SSL/TLS interception attempts
SIEM Query:
source="ISE" AND (event_type="api_request" AND status="failed") OR (process="unexpected_command")