VMware has released a patch to address a critical vulnerability in their vCenter Server software that could be leveraged by an attacker to execute arbitrary code on the server. Tracked as CVE-2021-21985, with a CVSS severity score of 9.8, the issue stems from a lack of input validation in the Virtual SAN (vSAN) Health Check plug-in, which is enabled by default in the vCenter Server. “A malicious actor with network access to port 443 may exploit this issue to execute commands with unrestricted privileges on the underlying operating system that hosts vCenter Server,” VMware said in its advisory. VMware vCenter Server is a server management utility that is used to control virtual machines, ESXi hosts, and other dependent components from a single centralized location. The flaw affects vCenter Server versions 6.5, 6.7, and 7.0 and Cloud Foundation versions 3.x and 4.x. VMware credited Ricter Z of 360 Noah Lab for reporting the vulnerability. “Organizations who have placed their vCenter Servers on networks that are directly accessible from the Internet […] should audit their systems for compromise,” VMware added. “They should also take steps to implement more perimeter security controls (firewalls, ACLs, etc.) on the management interfaces of their infrastructure.”
With the threat of ransomware looming nowadays the safest stance is to assume that an attacker may already have control of a desktop and a user account using techniques like phishing or spear phishing, and act accordingly. This means the attacker may already be able to reach vCenter Server from inside a corporate firewall, and time is of the essence. IT administrators should download and apply the patch as soon as possible to mitigate this threat.