CVE-2026-93084 firmware: arm_scmi: Drop handle on protocol bind failures

Not scored Published 17 Sep 2026 Updated 19 Oct 2026

A use-after-free vulnerability in the Linux kernel SCMI driver allows local attackers to cause denial of service or potentially execute code via race conditions during protocol binding failures.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2026-93084?

CVE-2026-93084 is an use after free vulnerability in Linux, published on 17 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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

firmware: arm_scmi: Drop handle on protocol bind failures

The SCMI bus notifier acquires an SCMI handle when the driver core emits BUS_NOTIFY_BIND_DRIVER, before invoking the protocol driver probe callback. The protocol probe path only checks whether sdev->handle is set.

If device_link_add() fails after the handle has been acquired, the protocol device can still bind with a valid handle but without the dependency link to the SCMI parent. A concurrent parent unbind can then miss the child and tear down the SCMI instance while the child still holds a handle into it.

If the protocol driver probe later fails, for example with -EPROBE_DEFER, the driver core emits BUS_NOTIFY_DRIVER_NOT_BOUND rather than BUS_NOTIFY_UNBOUND_DRIVER. The SCMI notifier only released the handle on BUS_NOTIFY_UNBOUND_DRIVER, so each failed protocol-device bind leaked the SCMI instance users refcount and left sdev->handle set after the failed probe.

Make the link helper report failure and drop the acquired handle if the link cannot be created. Also handle BUS_NOTIFY_DRIVER_NOT_BOUND in the same cleanup path used for unbind so failed probes balance the earlier BUS_NOTIFY_BIND_DRIVER acquisition.

Which versions are affected by CVE-2026-93084?

How do I fix CVE-2026-93084?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2026-93084 being exploited?

There is no known exploitation of CVE-2026-93084 in the wild and no public exploit code.

Sources

Also known as AZL-102044, BELL-CVE-2026-93084, DEBIAN-CVE-2026-93084, GHSA-mw9p-h9xr-r672, UBUNTU-CVE-2026-93084.