CVE-2021-4093

Published: 13 December 2021

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.

From the Ubuntu Security Team

Felix Wilhelm discovered that the KVM implementation in the Linux kernel did not properly handle exit events from AMD Secure Encrypted Virtualization-Encrypted State (SEV-ES) guest VMs. An attacker in a guest VM could use this to cause a denial of service (host kernel crash) or possibly execute arbitrary code in the host kernel.

Status

Severity score breakdown

References

• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-4093
• https://git.kernel.org/linus/95e16b4792b0429f1933872f743410f00e590c55 (5.15-rc7)
• https://ubuntu.com/security/notices/USN-5265-1
• NVD
• Launchpad
• Debian

Bugs

• https://bugzilla.redhat.com/show_bug.cgi?id=2028584