Ongoing VMware ESXi Ransomware Attack Highlights Inherent Virtualization Risks

Organizations using older versions of VMWare ESXi hypervisors are learning a hard lesson about staying up-to-date with vulnerability patching, as a global ransomware attack on what VMware has deemed "End of General Support (EOGS) and/or significantly out-of-date products" continues.

However, the onslaught also points out wider problems in locking down virtual environments, the researchers say.

VMware confirmed in a statement Feb. 6 that a ransomware attack first flagged by the French Computer Emergency Response Team (CERT-FR) on Feb. 3 is not exploiting an unknown or "zero-day" flaw, but rather previously identified vulnerabilities that already have been patched by the vendor.

Indeed, it was already believed that the chief avenue of compromise in an attack propagating a novel ransomware strain dubbed "ESXiArgs" is an exploit for a 2-year-old remote code execution (RCE) security vulnerability (CVE-2021-21974), which affects the hypervisor's Open Service Location Protocol (OpenSLP) service.

"With this in mind, we are advising customers to upgrade to the latest available supported releases of vSphere components to address currently known vulnerabilities," VMware told customers in the statement.

The company also recommended that customers disable the OpenSLP service in ESXi, something VMware began doing by default in shipped versions of the project starting in 2021 with ESXi 7.0 U2c and ESXi 8.0 GA, to mitigate the issue.

Unpatched Systems Again in the Crosshairs

VMware's confirmation means that the attack by as-yet unknown perpetrators that's so far compromised thousands of servers in Canada, France, Finland, Germany, Taiwan, and the US may have been avoided by something that all organizations clearly need to do better — patch vulnerable IT assets — security experts said.

"This just goes to show how long it takes many organizations to get around to patching internal systems and applications, which is just one of many reasons why the criminals keep finding their way in," notes Jan Lovmand, CTO for ransomware protection firm BullWall.

It's a "sad truth" that known vulnerabilities with an exploit available are often left unpatched, concurs Bernard Montel, EMEA technical director and security strategist for security exposure management firm Tenable.

"This puts organizations at incredible jeopardy of being successfully penetrated," he tells Dark Reading. "In this case, with the … VMWare vulnerability, the threat is immense given the active exploitation."

However, even given the risks of leaving vulnerable systems unpatched, it remains a complex issue for organizations to balance the need to update systems with the effect the downtime required to do so can have on a business, Montel acknowledges.

"The issue for many organizations is evaluating uptime, versus taking something offline to patch," he says. "In this case, the calculation really couldn’t be more straightforward — a few minutes of inconvenience, or days of disruption."

Virtualization Is Inherently a Risk

Other security experts don't believe the ongoing ESXi attack is as straightforward as a patching issue. Though lack of patching may solve the problem for some organizations in this case, it's not as simple as that when it comes to protecting virtualized environments in general, they note.

The fact of the matter is that VMware as a platform and ESXi in particular are complex products to manage from a security perspective, and thus easy targets for cybercriminals, says David Maynor, senior director of threat intelligence at cybersecurity training firm Cybrary. Indeed, multiple ransomware campaigns have targeted ESXi in the past year alone, demonstrating that savvy attackers recognize their potential for success.

Attackers get the added bonus with the virtualized nature of an ESXi environment that if they break into one ESXi hypervisor, which can control/have access to multiple virtual machines (VMs), "it could be hosting a lot of other systems that could also be compromised without any additional work," Maynor says.

Indeed, this virtualization that's at the heart of every cloud-based environment has made the task of threat actors easier in many ways, Montel notes. This is because they only have to target one vulnerability in one instance of a particular hypervisor to gain access to an entire network.

"Threat actors know that targeting this level with one arrow can allow them to elevate their privileges and grant access to everything," he says. "If they are able to gain access, they can push malware to infiltrate the hypervisor level and cause mass infection."

How to Protect VMware Systems When You Can't Patch

As the latest ransomware attack persists — with its operators encrypting files and asking for around 2 Bitcoin (or $23,000 at press time) to be delivered within three days of compromise or risk the release of sensitive data — organizations grapple with how to resolve the underlying issue that creates such a rampant attack.

Patching or updating any vulnerable systems immediately may not be entirely realistic, other approaches may need to be implemented, notes Dan Mayer, a threat researcher at Stairwell. "The truth is, there are always going to be unpatched systems, either due to a calculated risk taken by the organizations or due to resource and time constraints," he says.

The risk of having an unpatched system in and of itself may be mitigated then by other security measures, such as continuously monitoring enterprise infrastructure for malicious activity and being prepared to respond quickly and segment areas of attack if a problem arises.

Indeed, organizations need to act on the assumption that preventing ransomware "is all but impossible," and focus on putting tools in place "to lessen the impact, such as disaster recovery plans and context-switched data," notes Barmak Meftah, founding partner at cybersecurity venture capital firm Ballistic Ventures.

However, the ongoing VMware ESXi ransomware attack highlights another issue that contributes to an inherent inability for many organizations to take the necessary preventative measures: the skill and income gaps across the globe in the IT security realm, Mayer says.

"We do not have enough skilled IT professionals in nations where wealthy companies are targets," he tells Dark Reading. "At the same time, there are threat actors across the globe who are able to make a better living leveraging their skills to extort money from others than if they took legitimate cybersecurity work."

Mayer cites a report by the international cybersecurity nonprofit (ICS²) that said to secure assets effectively, the cybersecurity workforce needs 3.4 million cybersecurity workers. Until that happens, "we need to ramp up training these workers, and while the gap still exists, pay those with the skills around the world what they are worth, so they don’t turn to being part of the problem," Mayer says.