VMware is urging customers to immediately patch vulnerabilities in ESXi, Workstation, Fusion and Cloud Foundation running in on-premises or co-located settings.
The patches fix a total of five CVEs in those products that were disclosed during the Tianfu Cup, a Chinese security event that VMware participates in. According to the company, the flaws were reported to the Chinese government by the researchers that discovered them.
If organizations are unable to apply the patches, VMware says there is a workaround: removing the UB controllers from virtual machines. However, that may not be feasible at scale and doesn’t eliminate a potential threat like patching does.
“In short, patching VMware ESXi, Workstation, and Fusion are the fastest methods to resolve these issues,” the company said in a blog post.
VMWare advises that cloud-based VMware services are protected and fully operational, as are customers of VMware Cloud on AWS. No actions are needed to protect those workloads.
The VMware vulnerabilities include use-after-free bugs, double-fetch, unauthorized access and denial of service bugs.
According to VMWare, ESXi, Workstation and Fusion contain a user-after-free bug (CVE-2021-22040) in XHCI USB controller that could allow a bad actor with local admin privileges on a virtual machine to execute code as he virtual machine’s VMZ process running on the host.
Meanwhile, those three products also contain a double-fetch bug (CVE-2021-22041) that could also lead to unauthorized code execution on the virtual machine’s VMX process running on the host.
ESXi also contains a settingsd unauthorized access vulnerability (CVE-2021-22042) due to VMX having access to settingsd authorization tickets. A malicious actor with privileges in the VMX process only could access settingsd service running as a high priority user, the company says.
ESXi contains another vulnerability, this one a Time-of-check Time-of-use bug (CVE-2021-22043) that exists in the way temporary files ae handled that could be used to escalate privileges by writing arbitrary files.
The least dangerous ESXi flaw disclosed is a slow HTTP Post denial-of-service vulnerability in rhttpproxy that could be used to create a denial-of-service condition by overwhelming rhttpproxy service with multiple requests.
While the individual bugs don’t reach the critical level, VMware says the combined bugs should be treated as such because they can be combined to result in higher severity.
“The ramifications of this vulnerability are serious, especially if attackers have access to workloads inside your environments,” the company says.
For more information on workarounds and patching these vulnerabilities, read VMware’s advisory and the company’s associated blog.
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