VMware ESXi and Workstation: memory corruption flaw under attack

What is affected

VMware ESXi and Workstation is mostly run by companies, schools and public bodies, not on home computers. You are unlikely to have it yourself, but organisations that hold your data may. Breaches that start with flaws like this one are how personal data ends up leaked.

VMware ESXi and Workstation contain a time-of-check time-of-use (TOCTOU) race condition vulnerability that leads to an out-of-bounds write. Successful exploitation enables an attacker with local administrative privileges on a virtual machine to execute code as the virtual machine's VMX process running on the host.

What an attacker can do

This is a memory corruption flaw. It lets an attacker corrupt the program's memory by feeding it specially crafted content: a web page, a file or a network message. The result ranges from a crash to the attacker running their own code.

How it is reached

Needs access to the device or a file opened on it

Access the attacker needs

An administrator account

Does the victim have to do something?

No, works without the victim doing anything

What to do

1. At home: nothing to install. Keep your own devices updated and use a different password for every service, so that a breach at one organisation does not open your other accounts.
2. If you administer VMware ESXi and Workstation at work: apply the vendor's fix or mitigation now and review logs for signs of compromise, because the flaw was being exploited before it was listed.
3. If the product is past its support date and no fix exists, take it off the internet or retire it.

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Vendor advisories and fixes

• support.broadcom.comsupport.broadcom.com/web/ecx/support-content-notification/-/external/content/SecurityAdvis

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on March 4, 2025, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by March 25, 2025, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 1.6% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 74% of all scored vulnerabilities.

Its CVSS severity score is 8.2 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

VMware ESXi, and Workstation contain a TOCTOU (Time-of-Check Time-of-Use) vulnerability that leads to an out-of-bounds write. A malicious actor with local administrative privileges on a virtual machine may exploit this issue to execute code as the virtual machine's VMX process running on the host.