CVE-2025-40315 usb: gadget: f_fs: Fix epfile null pointer access after ep enable.
A race condition in the Linux kernel USB gadget functionfs driver causes a null pointer dereference, 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-2025-40315?
CVE-2025-40315 is a vulnerability in Linux, published on 8 Dec 2025. 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 epfile null pointer access after ep enable.
A race condition occurs when ffs_func_eps_enable() runs concurrently with ffs_data_reset(). The ffs_data_clear() called in ffs_data_reset() sets ffs->epfiles to NULL before resetting ffs->eps_count to 0, leading to a NULL pointer dereference when accessing epfile->ep in ffs_func_eps_enable() after successful usb_ep_enable().
The ffs->epfiles pointer is set to NULL in both ffs_data_clear() and ffs_data_close() functions, and its modification is protected by the spinlock ffs->eps_lock. And the whole ffs_func_eps_enable() function is also protected by ffs->eps_lock.
Thus, add NULL pointer handling for ffs->epfiles in the ffs_func_eps_enable() function to fix issues
Which versions are affected by CVE-2025-40315?
How do I fix CVE-2025-40315?
Apply the vendor's patch.
Is CVE-2025-40315 being exploited?
There is no known exploitation of CVE-2025-40315 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40315, DEBIAN-CVE-2025-40315, GHSA-xqq2-8462-xjg2, ROOT-OS-DEBIAN-12-CVE-2025-40315, ROOT-OS-DEBIAN-13-CVE-2025-40315, ROOT-OS-UBUNTU-2204-CVE-2025-40315 and 2 more.