CVE-2025-68786 ksmbd: skip lock-range check on equal size to avoid size==0 underflow
An integer underflow in the ksmbd kernel module can cause a denial of service when handling file locks with zero size.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-68786?
CVE-2025-68786 is a vulnerability in Linux, published on 13 Jan 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: skip lock-range check on equal size to avoid size==0 underflow
When size equals the current i_size (including 0), the code used to call check_lock_range(filp, i_size, size - 1, WRITE), which computes `size - 1` and can underflow for size==0. Skip the equal case.
Which versions are affected by CVE-2025-68786?
How do I fix CVE-2025-68786?
Apply the vendor's patch.
Is CVE-2025-68786 being exploited?
There is no known exploitation of CVE-2025-68786 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-68786, DEBIAN-CVE-2025-68786, GHSA-7vqw-4gww-392j, ROOT-OS-DEBIAN-12-CVE-2025-68786, ROOT-OS-DEBIAN-13-CVE-2025-68786, ROOT-OS-UBUNTU-2204-CVE-2025-68786 and 2 more.