More than 6,700 VMware vCenter Server systems are publicly accessible and vulnerable to a newly reported critical remote code execution (RCE) flaw that attackers are looking to exploit. 

Earlier this week, VMware released a security advisory when it patched two vulnerabilities in vCenter Server, a centralized management software for vSphere systems, as well as a flaw in the VMware ESXi hypervisor. CVE-2021-21972, the RCE vulnerability with a CVSSv3 score of 9.8, is the most severe. 

An unauthenticated attacker could exploit this by uploading a specially crafted file to an exposed vCenter Server endpoint that is publicly accessible over port 443, Tenable researchers explain in a blog post. If successful, the attacker could gain unrestricted RCE privileges in the underlying operating system of the vCenter Server.

While this vulnerability exists in the vRealize Operations vCenter plugiin, VMware's advisory states this plug-in is included in all default installations of the vCenter Server. 

Attackers are already scanning for vulnerable vCenter servers connected to the Internet, threat intelligence company Bad Packets reported on Twitter. Multiple proof-of-concept exploit scripts were published on GitHub, including one that can be configured for Windows and Linux targets.

Read the VMware advisory and Tenable analysis for more details.