CVE-2026-90232

/// Technical description

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

amt: Don't support cross-netns setup.

When a lower device is unregistered, amt_device_event() tries

to unregister its upper AMT device, but it has two problems.

1. amt_lookup_upper_dev() looks up an upper device in the

lower device's netns only

2. amt_device_event() unregisters a single upper device only

If AMT device is created on a lower device in another netns,

removing the lower device triggers the splat below and gets

stuck until all upper devices are removed. [0]

The cross-netns setup seems unintentional considering 1. and

the following points:

* amt_link_setup() sets dev->netns_immutable to true

* skb_scrub_packet() is not called in the fast path

* iproute2 binary fails to find cross-netns lower device via

link-netns:

# ip -n ns1 link add amt0 link-netns ns2 type amt dev veth1

Cannot find device "veth1"

Instead of supporting it properly and preparing for per-netns

netdev u

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References