CVE-2025-62623: Buffer Overflow in VMware ESXi

The heap-based buffer overflow vulnerability in VMware ESXi's ionic cloud driver presents a significant security risk. An attacker who successfully exploits this flaw could achieve privilege escalation, effectively gaining elevated access to the ESXi host. This could allow them to compromise the entire virtual infrastructure, including access to sensitive data stored on virtual machines. The potential for arbitrary code execution means an attacker could install malware, steal credentials, or disrupt critical services. Given ESXi's role as a hypervisor, the blast radius of this vulnerability is substantial, potentially impacting all virtual machines and applications running on the affected host. This vulnerability shares characteristics with other privilege escalation exploits targeting hypervisors, highlighting the importance of prompt patching.

1. Published2026-05-13

VMware has released a security advisory addressing CVE-2025-62623. The primary mitigation is to upgrade to a patched version of ESXi as soon as possible. If immediate patching is not feasible, consider implementing network segmentation to restrict access to the ESXi host. Review firewall rules to ensure only necessary traffic is allowed. Monitor ESXi logs for any unusual activity related to the ionic cloud driver. While a WAF or proxy cannot directly mitigate this vulnerability, they can help detect and block malicious traffic attempting to exploit it. After applying the upgrade, verify the fix by attempting to reproduce the vulnerability in a controlled environment using known exploit techniques (if available) or by reviewing VMware's testing documentation.