VMXNET3 heap overflow enabling guest-to-host escape in VMware ESXi. Actively exploited by LockBit 4.0 and Akira ransomware for mass hypervisor compromise.
| CVE ID | CVE-2026-21497 |
| Vendor | VMware |
| Affected Product | ESXi |
| Vulnerability Type | Hypervisor Escape / RCE |
| CVSS Score | 9.8 (CRITICAL) |
| Actively Exploited | ✅ Yes — CISA KEV Listed |
| Patch Available | VMSA-2026-0012 |
| Reported By | CYBERDUDEBIVASH SENTINEL APEX Intelligence |
Sigma rules, YARA signatures, IOC table, and SIEM queries for Splunk, Elastic, Sentinel, and Chronicle — deployable in 5 minutes.