CVE-2021-42133
📋 TL;DR
This vulnerability in Ivanti Avalanche allows attackers with access to the Inforail Service to write arbitrary files to the system. This could lead to remote code execution, data manipulation, or system compromise. Organizations running Ivanti Avalanche versions before 6.3.3 are affected.
💻 Affected Systems
- Ivanti Avalanche
📦 What is this software?
Avalanche by Ivanti
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise leading to data theft, ransomware deployment, or complete system takeover through arbitrary file writes that enable remote code execution.
Likely Case
Unauthorized file writes leading to data corruption, privilege escalation, or installation of backdoors for persistent access.
If Mitigated
Limited impact if proper network segmentation and access controls prevent unauthorized access to the Inforail Service.
🎯 Exploit Status
Exploitation requires access to the Inforail Service but is straightforward once 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 data. 3. Run the installer to upgrade to version 6.3.3. 4. Restart the Avalanche server and verify functionality.
🔧 Temporary Workarounds
Restrict Network Access to Inforail Service
allLimit network access to the Inforail Service port (typically TCP 1777) to only trusted management systems using firewall rules.
Windows Firewall: New-NetFirewallRule -DisplayName "Block Inforail" -Direction Inbound -Protocol TCP -LocalPort 1777 -Action Block
Linux iptables: iptables -A INPUT -p tcp --dport 1777 -j DROP
Implement Network Segmentation
allPlace Avalanche servers in isolated network segments with strict access controls to prevent unauthorized access.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Avalanche servers from untrusted networks.
- Apply principle of least privilege to service accounts and restrict file system permissions where possible.
🔍 How to Verify
Check if Vulnerable:
Check Avalanche version via the web interface (Admin > About) or by examining installed programs in Windows Control Panel.Check Version:
On Windows: wmic product where name="Avalanche" get versionVerify Fix Applied:
Verify version is 6.3.3 or higher in the Avalanche web interface and test that file write operations through Inforail are properly restricted.📡 Detection & Monitoring
Log Indicators:
- Unusual file write operations in Avalanche logs
- Access attempts to Inforail Service from unauthorized IPs
- Unexpected process creation following file writes
Network Indicators:
- Unusual traffic to TCP port 1777 (Inforail Service)
- Multiple failed authentication attempts followed by successful connections
SIEM Query:
source="avalanche_logs" AND (event="file_write" OR event="inforail_access") AND dest_port=1777