CVE-2021-3527: Debian Linux

Medium severity, CVSS 5.5. EPSS: 0.4% chance of exploitation in the next 30 days.

A flaw was found in the USB redirector device (usb-redir) of QEMU. Small USB packets are combined into a single, large transfer request, to reduce the overhead and improve performance. The combined size of the bulk transfer is used to dynamically allocate a variable length array (VLA) on the stack without proper validation. Since the total size is not bounded, a malicious guest could use this flaw to influence the array length and cause the QEMU process to perform an excessive allocation on the stack, resulting in a denial of service.

Affected products

• Debian Debian Linux: version 9.0 only; version 10.0 only
• Qemu Qemu: up to and including 6.0.0
• Red Hat Enterprise Linux: version 8.0 only

Published 2021-05-26. Last modified 2026-06-17.