CVE-2020-29569: Debian Linux

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

An issue was discovered in the Linux kernel through 5.10.1, as used with Xen through 4.14.x. The Linux kernel PV block backend expects the kernel thread handler to reset ring->xenblkd to NULL when stopped. However, the handler may not have time to run if the frontend quickly toggles between the states connect and disconnect. As a consequence, the block backend may re-use a pointer after it was freed. A misbehaving guest can trigger a dom0 crash by continuously connecting / disconnecting a block frontend. Privilege escalation and information leaks cannot be ruled out. This only affects systems with a Linux blkback.

Affected products

• Debian Debian Linux: version 9.0 only; version 10.0 only
• Linux Linux Kernel: from 4.1.44, before 4.2 (fixed in 4.2); from 4.4.80, before 4.4.254 (fixed in 4.4.254); from 4.9.36, before 4.9.249 (fixed in 4.9.249); from 4.11.9, before 4.12 (fixed in 4.12); from 4.12, before 4.14.213 (fixed in 4.14.213); from 4.15, before 4.19.164 (fixed in 4.19.164); …
• Netapp Hci Compute Node BIOS: affected versions not specified
• Netapp Solidfire & Hci Management Node: affected versions not specified
• Netapp Solidfire & Hci Storage Node: affected versions not specified
• Xen Xen: up to and including 4.14.1

Published 2020-12-15. Last modified 2026-06-17.