CVE-2025-41236 is a critical security vulnerability identified in VMware ESXi, Workstation, and Fusion products, specifically affecting the VMXNET3 virtual network adapter. The vulnerability is classified as an integer-overflow leading to an out-of-bounds write (CWE-787). This flaw allows a malicious actor who has local administrative privileges within a virtual machine configured with the VMXNET3 adapter to exploit the vulnerability to execute arbitrary code on the host system. The vulnerability does not affect virtual machines using other types of virtual network adapters. The integer overflow can cause memory corruption, enabling an attacker to escalate privileges from the guest VM to the host, compromising the hypervisor's integrity and potentially all hosted virtual machines. The CVSS v3.1 base score is 9.3, indicating a critical severity level, with a vector showing local attack vector, low attack complexity, no privileges required, no user interaction, and a scope change impacting confidentiality, integrity, and availability at a high level. No known exploits are currently reported in the wild, and no patches have been linked yet. The affected VMware versions include ESXi 7.0 and 8.0, which are widely deployed in enterprise environments for virtualization and cloud infrastructure.

For European organizations, this vulnerability poses a significant risk due to the widespread use of VMware ESXi in data centers, cloud service providers, and enterprise IT infrastructures. Exploitation could lead to full host compromise, allowing attackers to control multiple virtual machines, access sensitive data, disrupt services, and potentially move laterally within networks. This is particularly critical for sectors with stringent data protection requirements such as finance, healthcare, and government institutions within Europe. The ability to execute code on the host from a guest VM undermines the isolation guarantees of virtualization, threatening confidentiality, integrity, and availability of critical systems. Given the critical severity and the potential for privilege escalation without user interaction, the threat could facilitate advanced persistent threats (APTs) or ransomware attacks targeting European enterprises relying on VMware virtualization.

Immediate mitigation steps include restricting local administrative access within guest VMs to trusted personnel only, as exploitation requires local admin privileges on the VM. Organizations should audit and monitor VM configurations to identify and limit the use of the VMXNET3 virtual network adapter where possible. Network segmentation and strict access controls can reduce the risk of malicious insiders or compromised VMs exploiting this vulnerability. VMware customers should prioritize applying vendor patches once released and subscribe to VMware security advisories for updates. In the interim, consider disabling or replacing VMXNET3 adapters with alternative virtual network adapters if feasible, to mitigate exposure. Implement robust host and guest monitoring to detect anomalous behavior indicative of exploitation attempts. Additionally, enforce strict patch management policies and conduct vulnerability assessments focused on virtualization infrastructure.