CVE-2021-21538
📋 TL;DR
Dell EMC iDRAC9 versions 4.40.00.00 through 4.40.10.00 contain an improper authentication vulnerability that allows remote unauthenticated attackers to bypass authentication and gain access to the virtual console. This affects organizations using vulnerable iDRAC9 firmware for remote server management.
💻 Affected Systems
- Dell EMC iDRAC9
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of server management interface leading to unauthorized virtual console access, potential server takeover, and lateral movement within the network.
Likely Case
Unauthorized access to server management console allowing attackers to view sensitive system information, modify configurations, or disrupt operations.
If Mitigated
Limited impact if proper network segmentation and access controls prevent external access to iDRAC interfaces.
🎯 Exploit Status
Authentication bypass vulnerability that requires no user interaction and minimal technical skill to exploit.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.40.10.00 or later
Vendor Advisory: https://www.dell.com/support/kbdoc/000186420
Restart Required: Yes
Instructions:
1. Download iDRAC9 firmware version 4.40.10.00 or later from Dell Support. 2. Log into iDRAC web interface. 3. Navigate to Maintenance > System Update. 4. Upload and install the firmware update. 5. Reboot the iDRAC controller when prompted.
🔧 Temporary Workarounds
Network Segmentation
allRestrict network access to iDRAC interfaces using firewall rules or network segmentation.
Disable Virtual Console
allTemporarily disable virtual console access if not required for operations.
🧯 If You Can't Patch
- Implement strict network access controls to limit iDRAC interface access to trusted IP addresses only.
- Monitor iDRAC access logs for unauthorized authentication attempts and virtual console access.
🔍 How to Verify
Check if Vulnerable:
Check iDRAC firmware version via web interface (System > Overview > iDRAC Properties) or SSH (racadm getversion).Check Version:
racadm getversion | grep iDRACVerify Fix Applied:
Verify firmware version is 4.40.10.00 or later and test authentication requirements for virtual console access.📡 Detection & Monitoring
Log Indicators:
- Unauthenticated virtual console access attempts
- Successful virtual console sessions from unexpected IP addresses
Network Indicators:
- Unusual traffic patterns to iDRAC management ports (typically 443, 5900)
SIEM Query:
source="iDRAC" AND (event="Virtual Console" OR event="Authentication") AND user="anonymous"