CVE-2020-29569

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-12-15 · updated 2026-06-17
Weakness: CWE-416

Description

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 Linux: 9.0, 10.0
Linux kernel: from 4.1.44 before 4.2; from 4.4.80 before 4.4.254; from 4.9.36 before 4.9.249; from 4.11.9 before 4.12; from 4.12 before 4.14.213; from 4.15 before 4.19.164 — fixed in 4.12, 4.14.213, 4.19.164, 4.2, 4.4.254, 4.9.249
NetApp Hci Compute Node Bios: all versions
NetApp Solidfire & Hci Management Node: all versions
NetApp Solidfire & Hci Storage Node: all versions
xen: through 4.14.1

How to fix

Upgrade to a fixed version: Linux kernel 4.12, 4.14.213, 4.19.164, 4.2. Check the vendor advisory for mitigations.

References

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