According to cybersecurity companies, media reports and Microsoft itself, threat actors are actively exploiting security flaws in Azure’s Open Management Infrastructure framework that Microsoft disclosed as part of this months’ cumulative security updates.
The vulnerabilities are in the Open Management Infrastructure (OMI) framework, which Microsoft calls an open-source Web-Based Enterprise Management implementation for managing Linux and UNIX systems.
According to Microsoft, several Azure Virtual Machine (VM) management extensions use this framework to orchestrate configuration management and log collection on Linux VMs.
“The remote code execution vulnerability only impacts customers using a Linux management solution (on-premises SCOM or Azure Automation State Configuration or Azure Desired State Configuration extension) that enables remote OMI management,” the Microsoft Security Resource Center said in a blog post.
Microsoft says it has observed several active exploitation attempts, ranging from basic host enumeration to attempts to install a cryptocurrency miner or file share.
According to BleepingComputer, the OMI software agent is present on more than half of all Azure instances, and thousands of Azure customers and millions of endpoints could be impacted.
The website reported that by exploiting one of the remote code execution vulnerabilities, with a single packet, an attacker can become root on a remote machine by simply removing the authentication header.
The first attacks were spotted yesterday evening by security researcher Germán Fernández and were soon confirmed by cybersecurity companies GreyNoise and Bad Packets.
According to GreyNoise’s current stats, attackers are scanning the Internet for exposed Azure Linux VMs vulnerable to CVE-2021-38647 exploits from over 110 servers.
A Mirai botnet is behind some of these exploitation attempts targeting Azure Linux OMI endpoints vulnerable to CVE-2021-38647 RCE exploits, as first spotted by Fernández on Thursday evening.
Digital forensics firm Cado Security also analyzed the botnet malware dropped on compromised systems and found that it also “closes the ports of the vulnerabilities it exploited to stop other botnets taking over the system.”
According to Microsoft, customers must update vulnerable extensions for their Cloud and On-Premises deployments as the updates become available. Microsoft included an update schedule in its blog post.
For cloud deployments with auto update turned on, Microsoft will actively deploy the updates to extensions across Azure regions as per the schedule. The automatic extension updates will be transparently patched without a reboot. Where possible, customers should ensure that automatic extension updates are enabled.
The company says updates are already available for Azure Automation State Configuration (DSC), System Center Operations Manager (SCOM), Log Analytics agent to address the remote execution vulnerability (RCE) and Elevation of Privilege (EoP).
While updates are being rolled, Microsoft is urging customers to protect against the RCE vulnerability by ensuring VMs are deployed within a Network Security Group (NSG) or behind a perimeter firewall and restrict access to Linux systems that expose the OMI ports (TCP 5985, 5986, and 1270). Ports 5985 and 5986 are also used for PowerShell Remoting on Windows and are not impacted by these vulnerabilities, the company says.
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