CVE-2021-3748: Canonical Ubuntu Linux

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

A use-after-free vulnerability was found in the virtio-net device of QEMU. It could occur when the descriptor's address belongs to the non direct access region, due to num_buffers being set after the virtqueue elem has been unmapped. A malicious guest could use this flaw to crash QEMU, resulting in a denial of service condition, or potentially execute code on the host with the privileges of the QEMU process.

Affected products

• Canonical Ubuntu Linux: version 18.04 only; version 20.04 only; version 21.10 only
• Debian Debian Linux: version 9.0 only; version 10.0 only
• Fedoraproject Fedora: version 34 only
• Qemu Qemu: from 0.10.0, before 6.2.0 (fixed in 6.2.0)
• Red Hat Enterprise Linux: version 8.0 only
• Red Hat Enterprise Linux Advanced Virtualization Eus: version 8.4 only

Published 2022-03-23. Last modified 2026-06-17.