AZL-113314: CVE-2026-99286 affecting package kernel 6.6.161.1-1

Q: Which systems are exposed to this issue?

Systems running the affected Azure Linux kernel package version 6.6.161.1-1 with the Xen netback backend in use are implicated. The issue concerns cleanup after a XenBus connection failure or disconnect.

Q: What condition triggers the race?

The race occurs when statistics-reading paths observe a non-zero queue count after queue resources have become invalid during connection-failure cleanup. Those readers may then attempt to access invalid queues.

Q: How can I determine whether my system may be affected?

Check whether the installed kernel package is version 6.6.161.1-1 and whether the system uses the Xen netback backend. Review XenBus connection-failure or disconnect activity, particularly alongside accesses to netback statistics or ethtool statistics.

Published Nov 10, 2026

Updated

In the Linux kernel, the following vulnerability has been resolved:

xen-netback: Fix XenBus connection failure cleanup

xenvifgetstats and xenvifgetethtoolstats capture vif->numqueues under rcureadlock. We need to unpublish vif->numqueues before synchronizenet to ensure that readers that come afterwards will not read a non-zero vif->numqueues and attempt to access invalid queues.

This is the same cleanup algorithm as used in backenddisconnect and added in commit b17075d5c198 ("xen-netback: fix race condition on XenBus disconnect").

This is XSA-531

Affected Software

1 affected component

azure-linux/kernel<=6.6.161.1-1

Event History

Nov 10, 2026

Advisory Published

via OSV·07:22 PM

Data Sourced

via OSV·07:22 PM

DescriptionAffected Software

Child vulnerabilities

Contains the following vulnerabilities.

CVE-2026-99286

Frequently Asked Questions

Which systems are exposed to this issue?

Systems running the affected Azure Linux kernel package version 6.6.161.1-1 with the Xen netback backend in use are implicated. The issue concerns cleanup after a XenBus connection failure or disconnect.

What condition triggers the race?

The race occurs when statistics-reading paths observe a non-zero queue count after queue resources have become invalid during connection-failure cleanup. Those readers may then attempt to access invalid queues.

How can I determine whether my system may be affected?

Check whether the installed kernel package is version 6.6.161.1-1 and whether the system uses the Xen netback backend. Review XenBus connection-failure or disconnect activity, particularly alongside accesses to netback statistics or ethtool statistics.

AZL-113314: CVE-2026-99286 affecting package kernel 6.6.161.1-1

Affected Software

Event History

Child vulnerabilities

Frequently Asked Questions

Which systems are exposed to this issue?

What condition triggers the race?

How can I determine whether my system may be affected?

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Frequently Asked Questions

Which systems are exposed to this issue?

What condition triggers the race?

How can I determine whether my system may be affected?