CVE-2026-47876 is an out-of-bounds write vulnerability (CWE-787) in the VMXNET3 virtual network adapter of VMware ESX within Cloud Foundation versions 5.0.0 up to but not including 6.0.0. A local attacker with administrative privileges on a VM using the VMXNET3 adapter can exploit this flaw to execute arbitrary code on the host system. This vulnerability does not affect other virtual network adapters. The CVSS v3.1 base score is 9.3, reflecting critical severity with local attack vector, low attack complexity, no privileges required, no user interaction, and impacts to confidentiality, integrity, and availability. As of the published date, no official patch or remediation guidance has been provided by VMware.

Successful exploitation allows a local attacker with administrative privileges on a virtual machine using the VMXNET3 adapter to execute code on the host system, potentially compromising the host's confidentiality, integrity, and availability. This could lead to full host compromise from a guest VM context. Other virtual network adapters are not affected, limiting the scope to VMXNET3 users.

Patch status is not yet confirmed — check the VMware advisory for current remediation guidance. Until an official fix is available, restrict administrative access to virtual machines using the VMXNET3 adapter and monitor for suspicious activity. No vendor-provided mitigation or temporary fix is currently documented.