Security Experts:

Patch for Critical VMware ESXi Vulnerability Incomplete

VMware on Wednesday informed customers that it has released new patches for ESXi after learning that a fix made available last month for a critical vulnerability was incomplete.

The vulnerability, tracked as CVE-2020-3992, was described as a use-after-free bug that affects the OpenSLP service in ESXi. A remote, unauthenticated attacker can exploit the flaw to execute arbitrary code.

However, VMware said the attacker needs to be on the management network and have access to port 427 on an ESXi machine in order to exploit the flaw.

VMware learned about the security hole in July from Lucas Leong of Trend Micro's Zero Day Initiative (ZDI). An advisory was also published in October by ZDI.

“The specific flaw exists within the processing of SLP messages. The issue results from the lack of validating the existence of an object prior to performing operations on the object. An attacker can leverage this vulnerability to execute code in the context of the SLP daemon,” ZDI said.

VMware updated its initial advisory on Wednesday to inform customers that the patches had been incomplete. New fixes have now been released for ESXi 6.5, 6.7 and 7.0, but patches are still pending for VMware Cloud Foundation, the hybrid cloud platform for managing virtual machines and orchestrating containers.

VMware failing to patch a vulnerability on the first try is not unheard of. Earlier this year, the company made several attempts to patch a privilege escalation flaw affecting the macOS version of Fusion.

Related: Google Researcher Finds Vulnerability in VMware Virtualization Products

Related: VMware Cloud Director Vulnerability Has Major Impact for Cloud Providers

Related: VMware Again Fails to Patch Privilege Escalation Vulnerability in Fusion

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.