How to find VMware ESXi installations


Latest VMware ESXi vulnerabilities

On March 5th, 2024, VMware disclosed several vulnerabilities in its ESXi, Workstation, and Fusion products.

The vulnerabilities, reported as CVE-2024-22252, CVE-2024-22253, CVE-2024-22254, and CVE-2024-22255 allow code running inside virtual machines to access the host system in unauthorized ways.

The CVSS scores range from 7.1 (high) to 9.3 (critical); the vulnerabilities affecting ESXi are limited to high severity, but the vendor has indicated that taken together the vulnerabilities should be considered critical.

What is the impact? #

Upon successful exploitation of these vulnerabilities, an attacker who can execute code inside a virtual machine can access the host system and perform actions ranging from arbitrary code execution to sensitive information disclosure.

Are updates or workarounds available? #

VMware has released new versions of these products to address these vulnerabilities. All users are urged to update as quickly as possible.

How do I find potentially vulnerable VMware installations with runZero? #

From the Asset Inventory, use the following query to locate assets running potentially vulnerable versions of VMware ESXi or running VMware products:


Additionally, using the runZero VMware integration, use the following query to locate virtual machines running inside VMware, which could be potential sources of exploitation:


Additional fingerprinting research is ongoing, and additional queries will be published as soon as possible.

CVE-2021-21974 (February 2023) #

In February 2023, popular hypervisor ESXi made the news due to fresh targeting by a new strain of ransomware. Known as ESXiArgs, this ransomware leveraged a 2-year old heap overflow issue in the OpenSLP service that can be used to execute remote code on exploitable targets (CVE-2021-21974). Many vulnerable public-facing ESXi servers had already been affected by this malware (at the time over 1,900 via Censys search results).

What was the impact? #

Targets of this new ransomware campaign were older ESXi servers running certain versions of 6.5, 6.7, or 7 releases and also had the OpenSLP service enabled (it has not been enabled by default in ESXi releases since 2021). Upon successful exploitation of CVE-2021-21974, the ESXiArgs ransomware encrypted a number of file types on the target system, including VM-related files with extensions .vmxf, .vmx, .vmdk, .vmsd, and .nvram. Ransom notes were saved as HTML files on compromised systems for admins and users to subsequently discover. While some of these ransom notes claim to have stolen data from vulnerable targets, no data exfiltration had been observed at the time.

VMware made patches available when the OpenSLP heap-overflow vulnerability was initially reported in 2021. The following ESXi releases had been patched against this attack vector and exploited by the ESXiArgs campaign:

  • ESXi version 7+ (ESXi70U1c-17325551 and later)
  • ESXi version 6.7+ (ESXi670-202102401-SG and later)
  • ESXi version 6.5+ (ESXi650-202102101-SG and later)

VMware also offered patched releases for Cloud Foundation (ESXi), which included an ESXi component:

  • Cloud Foundation (ESXi) version 4.2+
  • Patching instructions for Cloud Foundation (ESXi) version 3.x can be found here

Patching (and also ensuring that your ESXi servers were running a supported, not end-of-life/end-of-support version) was the best course of action. If patching was not a near-term option, VMware recommended mitigation via disabling the OpenSLP service.

Written by Rob King

Rob King is the Director of Security Research at runZero. Over his career Rob has served as a senior researcher with KoreLogic, the architect for TippingPoint DVLabs, and helped get several startups off the ground. Rob helped design SC Magazine's Data Leakage Prevention Product of the Year for 2010, and was awarded the 3Com Innovator of the Year Award in 2009. He has been invited to speak at BlackHat, Shmoocon, SANS Network Security, and USENIX.

More about Rob King

Written by Pearce Barry

More about Pearce Barry
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