CVE-2021-4093: Canonical Ubuntu Linux

High severity, CVSS 8.8. EPSS: 0.4% chance of exploitation in the next 30 days.

A flaw was found in the KVM's AMD code for supporting the Secure Encrypted Virtualization-Encrypted State (SEV-ES). A KVM guest using SEV-ES can trigger out-of-bounds reads and writes in the host kernel via a malicious VMGEXIT for a string I/O instruction (for example, outs or ins) using the exit reason SVM_EXIT_IOIO. This issue results in a crash of the entire system or a potential guest-to-host escape scenario.

Affected products

• Canonical Ubuntu Linux: version 20.04 only; version 21.10 only
• Fedoraproject Fedora: version 35 only
• Linux Linux Kernel: from 5.11, before 5.14.16 (fixed in 5.14.16)
• Red Hat Enterprise Linux: version 8.0 only

Published 2022-02-18. Last modified 2026-06-17.