CVE-2025-41236 is a critical integer-overflow vulnerability identified in VMware ESXi, Workstation, and Fusion products specifically affecting the VMXNET3 virtual network adapter. The vulnerability arises from an out-of-bounds write condition (CWE-787) triggered by an integer overflow within the VMXNET3 adapter's processing logic. This flaw allows a malicious actor who already has local administrative privileges within a virtual machine configured with the VMXNET3 adapter to execute arbitrary code on the underlying host system. Notably, virtual machines using other types of virtual network adapters are not impacted by this vulnerability. The vulnerability affects VMware ESXi versions 7.0 and 8.0. The CVSS v3.1 base score is 9.3, indicating a critical severity level, with an attack vector classified as local (AV:L), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and a scope change (S:C) that impacts confidentiality, integrity, and availability at a high level (C:H/I:H/A:H). Although no known exploits are currently reported in the wild, the potential for host compromise from a guest VM makes this vulnerability particularly dangerous in multi-tenant or cloud environments where ESXi hosts run multiple virtual machines. The lack of patch links suggests that remediation may still be pending or in progress, emphasizing the need for immediate attention from VMware customers using affected versions and VMXNET3 adapters.

For European organizations, the impact of CVE-2025-41236 is significant, especially for enterprises and service providers relying on VMware ESXi for virtualization infrastructure. Successful exploitation could lead to full host compromise, allowing attackers to escape the virtual machine sandbox, access sensitive data across multiple VMs, disrupt services, or deploy further malware at the hypervisor level. This risk is amplified in data centers, cloud providers, and critical infrastructure sectors where VMware ESXi is widely deployed. Confidentiality breaches could expose personal data protected under GDPR, leading to regulatory penalties and reputational damage. Integrity and availability impacts could disrupt business operations, cause downtime, and affect dependent services. The requirement for local administrative privileges on a VM limits the attack surface to insiders or attackers who have already compromised a guest VM, but the absence of user interaction and low complexity means that once inside, attackers can reliably escalate privileges to the host. This elevates the threat level for organizations with multi-tenant environments, managed service providers, and enterprises using VMXNET3 adapters extensively.

1. Immediate assessment of VMware ESXi, Workstation, and Fusion deployments to identify virtual machines using the VMXNET3 virtual network adapter. 2. Restrict and monitor administrative access within guest VMs to minimize the risk of local privilege escalation attempts. 3. Implement network segmentation and strict access controls to limit lateral movement from compromised VMs. 4. Apply VMware security advisories and patches as soon as they become available; in the absence of official patches, consider temporary workarounds such as disabling or replacing VMXNET3 adapters with alternative virtual network adapters where feasible. 5. Enhance host-level monitoring and intrusion detection to identify suspicious activities indicative of exploitation attempts. 6. Conduct regular vulnerability scanning and penetration testing focusing on virtualization infrastructure. 7. Educate internal teams about the risks of local VM compromise leading to host takeover to improve operational security practices. 8. Maintain up-to-date backups and incident response plans tailored for virtualization environments to ensure rapid recovery in case of exploitation.