CVE-2026-93093 firmware: arm_scmi: Publish channel state before callbacks
A race condition in the Linux kernel SCMI driver allows a NULL pointer dereference, leading to a system crash or denial of service.
- 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-2026-93093?
CVE-2026-93093 is a 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: Publish channel state before callbacks
Transport setup can enable callbacks before the setup routine returns. mailbox_chan_setup() registers the mailbox client with mbox_request_channel(), and the mailbox controller startup path can enable interrupt delivery before SCMI mailbox channel state has been published. Similarly, smc_chan_setup() requests the optional A2P completion IRQ before the SMC transport has made its cinfo pointer visible.
If a pending or spurious callback fires in those windows, the transport RX callback can dereference a NULL transport cinfo pointer. Publishing only the transport-private pointer is not sufficient either: an early callback can enter the SCMI core before scmi_chan_setup() has assigned cinfo->handle. The core derives scmi_info from cinfo->handle in the RX path, so a NULL handle can still fault even when the transport-private cinfo is valid.
Assign cinfo->handle before invoking the transport setup callback. Publish the mailbox and SMC transport-private channel state before requesting the mailbox channels or IRQ, and clear the early-published pointers again on setup failure. Also unwind mailbox setup devres resources on failure so an optional RX setup error that is ignored by the core does not leave stale transport state behind.
Which versions are affected by CVE-2026-93093?
How do I fix CVE-2026-93093?
Apply the vendor's patch.
Is CVE-2026-93093 being exploited?
There is no known exploitation of CVE-2026-93093 in the wild and no public exploit code.
Sources
Also known as AZL-110444, BELL-CVE-2026-93093, DEBIAN-CVE-2026-93093, GHSA-wj2w-288c-r9m4, UBUNTU-CVE-2026-93093.