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In September 2021, Mirai was reported attempting to exploit OMIGOD, an unauthenticated remote-code-execution flaw in Open Management Infrastructure (OMI). Microsoft had released fixes for the flaw and three other OMI vulnerabilities on September 14; its security response team published additional Azure VM management-extension guidance on September 16. The report of Mirai activity followed on September 17—it is historical, not evidence of current exploitation in 2026.
What OMIGOD was—and what Mirai reportedly did
OMI is an open-source Web-Based Enterprise Management implementation used to manage Linux and UNIX systems. Microsoft said some Azure VM management extensions use OMI for configuration management and log collection. The OMIGOD name refers to CVE-2021-38647, an unauthenticated remote-code-execution vulnerability.
On September 14, 2021, Microsoft released fixes for that flaw and three OMI elevation-of-privilege vulnerabilities: CVE-2021-38645, CVE-2021-38649, and CVE-2021-38648. Two days later, the Microsoft Security Response Center (MSRC) issued additional guidance for Azure VM management extensions. On September 17, SecurityWeek reported that researchers had seen Mirai attempting to compromise vulnerable systems and closing TCP port 5896, which the report identified as OMI’s SSL port. The report suggested this could keep other attackers out, but did not establish the campaign’s scale or whether it remains active.
Which Linux systems were at risk?
Not every Azure Linux VM was necessarily vulnerable. Microsoft said the remote-code-execution risk applied to customers using Linux management solutions that enabled remote OMI management, including on-premises System Center Operations Manager (SCOM), Azure Automation State Configuration, and the Azure Desired State Configuration extension. Exposure depended on the installed OMI or extension version and deployment configuration.
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MSRC’s September 2021 guidance said all OMI versions below v1.6.8-1 were vulnerable. The advisory covered standalone OMI as well as management components and extensions, including SCOM, Azure Automation State Configuration/DSC, Log Analytics Agent, Azure Diagnostics, Azure Automation Update Management, Azure Automation, Azure Security Center, Azure Sentinel, Container Monitoring Solution, Azure Stack Hub components, and Azure HDInsight. Fixed versions differed by component, so v1.6.8-1 should not be treated as a universal extension version.
How administrators were advised to check and remediate
Microsoft’s guidance was to identify affected systems, compare each installed component with the advisory’s component-specific fixed version, and update where necessary. Use Microsoft’s OMI vulnerability advisory for the version table rather than assuming that all extensions share one update or version.
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- Inventory the deployment. Identify whether the system is an Azure VM, an Azure Stack Hub deployment, or an on-premises Linux system, then record its OMI version and installed management extensions or agents.
- Compare versions by component. Check each installed item against the fixed version listed for that specific component in Microsoft’s advisory. The standalone OMI version and extension versions are not interchangeable.
- Apply the relevant update. Microsoft advised updating vulnerable extensions in cloud and on-premises deployments, and enabling automatic extension upgrades where possible. The September 2021 bulletin said extension updates had been deployed across regions and that automatic updates could apply without a reboot; it also described cases needing manual remediation. Those were statements about the 2021 rollout, not assurances about a current fleet.
- Verify completion. Confirm that the installed component reached its applicable fixed version and that any required manual remediation was completed. Microsoft’s bulletin listed Azure Portal, Azure CLI, and a scan script as ways to identify affected VMs; follow the advisory’s instructions for the relevant deployment.
Reduce network exposure to OMI
As defense in depth, MSRC advised placing VMs behind a Network Security Group or perimeter firewall and restricting access to TCP ports 5985, 5986, and 1270 on Linux systems exposing OMI. Microsoft’s threat entry likewise advises updating affected components and restricting those ports. Port 5896 is distinct: it is the port SecurityWeek said Mirai was closing in its contemporaneous report, not one of the three ports in MSRC’s restriction guidance.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the September 2021 report does—and does not—establish
The historical reporting establishes that Mirai exploitation attempts were observed at the time and that Microsoft published remediation guidance. It does not provide an affected-device count, measure how widespread the attempts were, or establish that the activity continues today. Administrators assessing systems now should use current Microsoft guidance and verify their actual installed OMI and extension versions rather than infer present-day exposure from the 2021 report.
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