As the presence of the agent is unknown to the owner of the VM, and Microsoft has no auto update mechanism for these agents, it has to be manually upgraded, British security expert Kevin Beaumont said in a tweet.
"...so now you need to manually upgrade the agents you didn’t know existed as you didn’t install them," Beaumont, who formerly worked as a threat researcher for the Redmond giant, added, with a touch of sarcasm.
As the agent is known as Open Management Infrastructure or OMI, Nir Ohfeld of Wiz gave the vulnerability the catchy name OMIGOD. The agent runs as root, with the maximum privileges.
What's going on at Microsoft? pic.twitter.com/UMCYrdga2S— Ryan Naraine (@ryanaraine) September 15, 2021
Ohfeld said the OMI agent was embedded in many popular Azure services.
"When customers set up a Linux virtual machine in their cloud, the OMI agent is automatically deployed without their knowledge when they enable certain Azure services," he explained.
"Unless a patch is applied, attackers can easily exploit these four vulnerabilities to escalate to root privileges and remotely execute malicious code (for instance, encrypting files for ransom).
"We named this quartet of zero-days 'OMIGOD' because that was our reaction when we discovered them. We conservatively estimate that thousands of Azure customers and millions of endpoints are affected. In a small sample of Azure tenants we analyzed, over 65% were unknowingly at risk."
This is even more severe. The RCE is the simplest RCE you can ever imagine. Simply remove the auth header and you are root. remotely. on all machines. Is this really 2021? pic.twitter.com/iIHNyqgew4— Ami Luttwak (@amiluttwak) September 14, 2021
More than half of all Azure instances run Linux as a VM, according to Microsoft.
Ohfeld said these VMs were at risk if they were running any of the following services or tools:
- Azure Automation
- Azure Automatic Update
- Azure Operations Management Suite
- Azure Log Analytics
- Azure Configuration Management
- Azure Diagnostics
He hastened to add that this was just a partial list, and invited Azure users to contact him if they were aware of other services running OMI.
But Linux VMs were not the only source of worry. "In addition to Azure cloud customers, other Microsoft customers are affected since OMI can be independently installed on any Linux machine and is frequently used on-premise," Ohfeld pointed out.
"For example, OMI is built in System Center for Linux, Microsoft’s server management solution."
Azure broke the shared responsibility model with OMI and the #omigod vulnerabilities expose these cracks. Customers have to patch a CVSS 9.8 vulnerability in a software they don't even know that's installed in their environment pic.twitter.com/peOpE8GNTS— Al (@41thexplorer) September 15, 2021
Ami Luttwak, the chief technology officer of Wiz.io, said: "The RCE is the simplest RCE you can ever imagine. Simply remove the auth header and you are root. remotely. on all machines.
And he added, sarcastically, "Is this really 2021?"
In his post, Ohfeld wrote: "This is a textbook RCE vulnerability that you would expect to see in the 90s – it’s highly unusual to have one crop up in 2021 that can expose millions of endpoints. With a single packet, an attacker can become root on a remote machine by simply removing the authentication header. It’s that simple.
Microsoft also need to fix this one. The OMSagent (Sentinel etc) has an LPE to root. pic.twitter.com/9qJfWo5EYj— Kevin Beaumont (@GossiTheDog) September 14, 2021
"Thanks to the combination of a simple conditional statement coding mistake and an uninitialised auth struct, any request without an Authorisation header has its privileges default to uid=0, gid=0, which is root."
He said the company had reported the four vulnerabilities to Microsoft and they had been patched effective September 14 US time.
"Upgrading OMI happens through the parent Azure service that installed it. However, we urge customers to verify that their environment is indeed patched and they are running the latest version of OMI (Version 22.214.171.124)," Ohfeld added.