CVE-2021-42124
📋 TL;DR
This vulnerability allows an attacker with access to the Inforail Service in Ivanti Avalanche to perform session takeover, potentially gaining unauthorized access to the system. It affects Ivanti Avalanche versions before 6.3.3. Organizations using vulnerable versions are at risk of compromise.
💻 Affected Systems
- Ivanti Avalanche
📦 What is this software?
Avalanche by Ivanti
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attacker to take over administrative sessions, access sensitive data, and potentially deploy ransomware or other malware across managed devices.
Likely Case
Unauthorized access to the Avalanche management console, allowing configuration changes, data exfiltration, or deployment of malicious payloads to managed endpoints.
If Mitigated
Limited impact due to network segmentation and strong authentication controls preventing access to the Inforail Service.
🎯 Exploit Status
Exploitation requires access to the Inforail Service but appears to be straightforward once that access is obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.3.3
Vendor Advisory: https://forums.ivanti.com/s/article/Security-Alert-CVE-s-Addressed-in-Avalanche-6-3-3
Restart Required: Yes
Instructions:
1. Download Avalanche 6.3.3 from Ivanti support portal. 2. Backup current configuration and database. 3. Run the installer to upgrade to version 6.3.3. 4. Restart the Avalanche server and verify functionality.
🔧 Temporary Workarounds
Network Segmentation
allRestrict access to the Inforail Service using firewall rules to only allow connections from trusted sources.
Access Control Lists
allImplement strict network ACLs to limit which IP addresses can communicate with the Avalanche server on Inforail Service ports.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate the Avalanche server from untrusted networks
- Monitor for unusual authentication patterns or session activity in Avalanche logs
🔍 How to Verify
Check if Vulnerable:
Check the Avalanche version in the web interface under Help > About, or check the installed version in Windows Programs and Features.Check Version:
Not applicable - check via web interface or Windows control panelVerify Fix Applied:
Verify version shows 6.3.3 or later in the Avalanche web interface or installed programs list.📡 Detection & Monitoring
Log Indicators:
- Unusual session creation patterns
- Multiple failed authentication attempts followed by successful login from same source
- Administrative actions from unexpected IP addresses
Network Indicators:
- Unusual traffic patterns to Inforail Service ports (typically TCP 1777)
- Connection attempts from unauthorized IP ranges
SIEM Query:
source="avalanche_logs" AND (event_type="session_takeover" OR (auth_failure AND auth_success) FROM same_ip WITHIN 5m)