Pierluigi Paganini February 07, 2023

VMware said there is no evidence that threat actors are exploiting a zero-day flaw in its software as part of an ongoing ESXiArgs ransomware campaign.

VMware said that it found no evidence that the threat actors behind the ongoing ESXiArgs ransomware attacks are leveraging a zero-day vulnerability in VMware ESXi servers.

“VMware has not found evidence that suggests an unknown vulnerability (0-day) is being used to propagate the ransomware used in these recent attacks.” reads the latest advisory published by the company. “Most reports state that End of General Support (EOGS) and/or significantly out-of-date products are being targeted with known vulnerabilities which were previously addressed and disclosed in VMware Security Advisories (VMSAs).” 

ESXi is VMware’s hypervisor, a technology that allows organizations to host several virtualized computers running multiple operating systems on a single physical server. The Computer Emergency Response Team of France (CERT-FR) was the first to notice and send an alert about the attack. Italy’s National Cybersecurity Agency (ACN) and Cyber Security Agency of Singapore have also issued warnings for organizations to take immediate action to protect their systems.

Researchers from GreyNoise reported that 19 IP addresses have been observed attempting to exploit CVE-2021-21974.

The French Computer Emergency Response Team (CERT-FR) warned that threat actors are targeting VMware ESXi servers to deploy ransomware.

CERT-FR reported that threat actors behind these ransomware attackers are actively exploiting the vulnerability CVE-2021-21974.

The vulnerability is an OpenSLP heap-overflow flaw in VMware ESXi that can be exploited by attackers to execute arbitrary code remotely on vulnerable devices. The vulnerability affects the following systems:

• ESXi 7.x versions earlier than ESXi70U1c-17325551
• ESXi versions 6.7.x earlier than ESXi670-202102401-SG
• ESXi versions 6.5.x earlier than ESXi650-202102101-SG

The virtualization giant addressed the CVE-2021-21974 bug in February 2021.

“On February 3, 2023, CERT-FR became aware of attack campaigns targeting VMware ESXi hypervisors with the aim of deploying ransomware on them.” reads the alert published by CERT-FR. “In the current state of investigations , these attack campaigns seem to exploit the CVE-2021-21974 vulnerability, for which a patch has been available since February 23, 2021. This vulnerability affects the Service Location Protocol ( SLP ) service and allows a attacker to remotely exploit arbitrary code. The systems currently targeted would be ESXi hypervisors in version 6.x and prior to 6.7.”

CERT-FR urges applying all patches available for the ESXi hypervisor, it also recommends performing a system scan to detect any signs of compromise.

The virtualization giant also recommends disabling the SLP service on ESXi hypervisors that have not been updated.

“With this in mind, we are advising customers to upgrade to the latest available supported releases of vSphere components to address currently known vulnerabilities.” continues the latest advisory. “In addition, VMware has recommended disabling the OpenSLP service in ESXi since 2021 when ESXi 7.0 U2c and ESXi 8.0 GA began shipping with the service disabled by default.” c

VMware also informs its customers it has general ransomware resources available at our Ransomware Resource Center.

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Pierluigi Paganini

(SecurityAffairs – hacking, VMware)