CVE-2026-93829 smb: client: fix races in cifsd thread creation
A race condition in the Linux kernel SMB client allows remote attackers to cause a denial of service by triggering a thread synchronization error.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-93829?
CVE-2026-93829 is a vulnerability in Linux, published on 24 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix races in cifsd thread creation
The cifsd demultiplex thread can run and access tcp_ses before the parent thread has finished populating tcp_ses, which the worker thread accesses locklessly.
Also, the kthread_run macro may start the thread before returning the thread pointer. Because the pointer is part of the structure that the thread can access, if the kernel is preempted after the thread is spawned, but before the thread pointer is populated and the thread attempts to exit, it will sleep, waiting for a SIGKILL signal.
Fix this by moving creation of the thread to after all of tcp_ses'es fields are populated, and spawning the thread last, using a split kthread_create/wake_up_process logic.
Which versions are affected by CVE-2026-93829?
How do I fix CVE-2026-93829?
Apply the vendor's patch.
Is CVE-2026-93829 being exploited?
There is no known exploitation of CVE-2026-93829 in the wild and no public exploit code.
Sources
Also known as AZL-103769, BELL-CVE-2026-93829, DEBIAN-CVE-2026-93829, GHSA-v43p-8x6p-65w4, UBUNTU-CVE-2026-93829.