CVE-2026-93121 usb: gadget: f_fs: Fix fence cleanup in ffs_dmabuf_transfer() error paths
A flaw in the Linux kernel USB gadget driver causes undefined behavior when handling specific error paths, potentially leading to a system crash.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-93121?
CVE-2026-93121 is a high-severity 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:
usb: gadget: f_fs: Fix fence cleanup in ffs_dmabuf_transfer() error paths
The error paths for endpoint-disabled (ESHUTDOWN) and request-allocation failure (ENOMEM) in ffs_dmabuf_transfer() jump to err_fence_put which calls dma_fence_put() on the fence. However, at that point the fence has only been kmalloc'd — dma_fence_init() has not been called yet, so the refcount and the fence ops are uninitialized. Calling dma_fence_put() on such an object leads to undefined behavior.
Use kfree() instead, since the fence is just a plain allocation at this stage, and rename the label to err_fence_free to reflect the actual cleanup action.
Which versions are affected by CVE-2026-93121?
How do I fix CVE-2026-93121?
Apply the vendor's patch.
Is CVE-2026-93121 being exploited?
There is no known exploitation of CVE-2026-93121 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-93121, DEBIAN-CVE-2026-93121, GHSA-vg86-rjrh-q8jw, UBUNTU-CVE-2026-93121.