CVE-2021-38647
📋 TL;DR
CVE-2021-38647 is an authentication bypass vulnerability in Microsoft's Open Management Infrastructure (OMI) that allows unauthenticated attackers to execute arbitrary code with root privileges. This affects Azure Linux virtual machines and on-premises Linux systems running OMI. The vulnerability is particularly dangerous because it can be exploited remotely without credentials.
💻 Affected Systems
- Microsoft Open Management Infrastructure (OMI)
- Azure Linux Virtual Machines
- System Center Operations Manager (SCOM)
- Azure Automation
- Azure Log Analytics
📦 What is this software?
Azure Automation State Configuration by Microsoft
View all CVEs affecting Azure Automation State Configuration →
Azure Automation Update Management by Microsoft
View all CVEs affecting Azure Automation Update Management →
Azure Open Management Infrastructure by Microsoft
View all CVEs affecting Azure Open Management Infrastructure →
Azure Sentinel by Microsoft
Azure Stack Hub by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with root-level access, enabling data theft, ransomware deployment, lateral movement, and persistent backdoor installation across affected infrastructure.
Likely Case
Remote code execution leading to cryptocurrency mining, credential harvesting, or initial access for further attacks on cloud and enterprise environments.
If Mitigated
Limited impact with proper network segmentation, minimal exposure, and strong monitoring, though risk remains significant due to the authentication bypass nature.
🎯 Exploit Status
Multiple public exploits exist, and the vulnerability has been actively exploited in the wild. The authentication bypass makes exploitation trivial for attackers with network access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: OMI version 1.6.8-1 or later
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-38647
Restart Required: Yes
Instructions:
1. Update OMI to version 1.6.8-1 or later. 2. For Azure VMs: Apply Azure Security Center recommendations or update via package manager. 3. For on-premises: Use system package manager (apt/yum) to update OMI. 4. Restart affected services or systems.
🔧 Temporary Workarounds
Network Access Control
linuxRestrict access to OMI ports (5985, 5986, 1270) using firewall rules to only trusted sources.
sudo iptables -A INPUT -p tcp --dport 5985 -j DROP
sudo iptables -A INPUT -p tcp --dport 5986 -j DROP
sudo iptables -A INPUT -p tcp --dport 1270 -j DROP
Disable OMI Service
linuxTemporarily disable OMI service if not required, though this may break management functionality.
sudo systemctl stop omi
sudo systemctl disable omi
🧯 If You Can't Patch
- Implement strict network segmentation and firewall rules to block all access to OMI ports from untrusted networks.
- Deploy intrusion detection systems (IDS) and endpoint detection and response (EDR) solutions to monitor for exploitation attempts and anomalous process execution.
🔍 How to Verify
Check if Vulnerable:
Check OMI version with: omicli -v or dpkg -l omi | grep ^iiCheck Version:
omicli -v 2>/dev/null || dpkg -l omi 2>/dev/null || rpm -qa | grep omiVerify Fix Applied:
Verify OMI version is 1.6.8-1 or later: omicli -v | grep -q '1.6.8-1' && echo 'Patched'📡 Detection & Monitoring
Log Indicators:
- Unusual authentication attempts on OMI ports
- Suspicious process execution from OMI service
- Failed authentication logs followed by successful access
Network Indicators:
- Unexpected connections to ports 5985, 5986, 1270
- Traffic patterns indicating exploitation attempts
SIEM Query:
source="*omi*" OR port IN (5985, 5986, 1270) AND (event_type="authentication_failure" OR process_execution="suspicious")🔗 References
- http://packetstormsecurity.com/files/164694/Microsoft-OMI-Management-Interface-Authentication-Bypass.html
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-38647
- http://packetstormsecurity.com/files/164694/Microsoft-OMI-Management-Interface-Authentication-Bypass.html
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-38647
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-38647
