CVE-2021-38649
📋 TL;DR
CVE-2021-38649 is an elevation of privilege vulnerability in Microsoft's Open Management Infrastructure (OMI) agent on Linux systems. It allows authenticated attackers to execute arbitrary code with root privileges by exploiting improper input validation. This affects Linux systems running OMI agent versions 1.6.8-1 and earlier.
💻 Affected Systems
- Microsoft Open Management Infrastructure (OMI)
📦 What is this software?
Azure Automation State Configuration by Microsoft
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Azure Automation Update Management by Microsoft
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Azure Open Management Infrastructure by Microsoft
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Azure Sentinel by Microsoft
Azure Stack Hub by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with root-level code execution, enabling attackers to install persistent backdoors, steal sensitive data, or pivot to other systems.
Likely Case
Privilege escalation from authenticated user to root, allowing attackers to modify system configurations, install malware, or access restricted data.
If Mitigated
Limited impact if proper network segmentation, least privilege access, and monitoring are in place to detect and contain exploitation attempts.
🎯 Exploit Status
Exploitation requires authentication but is straightforward once access is obtained. Actively exploited in the wild.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: OMI version 1.6.8-2 or later
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-38649
Restart Required: Yes
Instructions:
1. Update OMI agent to version 1.6.8-2 or later. 2. For Azure Linux VMs, apply updates via Azure Update Management or package manager. 3. For on-premises systems, download and install updated OMI packages from Microsoft. 4. Restart affected services or systems.
🔧 Temporary Workarounds
Network Segmentation
linuxRestrict network access to OMI ports (typically 5985, 5986, 1270) to trusted management systems only.
iptables -A INPUT -p tcp --dport 5985 -s trusted_ip -j ACCEPT
iptables -A INPUT -p tcp --dport 5985 -j DROP
Disable OMI Service
linuxTemporarily disable OMI service if not required, but this may break management functionality.
systemctl stop omi
systemctl disable omi
🧯 If You Can't Patch
- Implement strict network access controls to limit OMI port exposure
- Apply principle of least privilege to user accounts and monitor for suspicious authentication attempts
🔍 How to Verify
Check if Vulnerable:
Run: omi --version and check if version is 1.6.8-1 or earlierCheck Version:
omi --versionVerify Fix Applied:
Run: omi --version and confirm version is 1.6.8-2 or later📡 Detection & Monitoring
Log Indicators:
- Unusual authentication patterns to OMI service
- Process execution with elevated privileges from OMI context
- Modifications to OMI configuration files
Network Indicators:
- Unexpected connections to OMI ports (5985, 5986, 1270) from unauthorized sources
- Anomalous traffic patterns to OMI endpoints
SIEM Query:
source="omi.log" AND (event="authentication" OR event="privilege") AND result="success" | stats count by src_ip, user