CVE-2025-40291 io_uring: fix regbuf vector size truncation
An integer overflow in the Linux kernel's io_uring subsystem can lead to memory corruption and potential denial of service.
- 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-2025-40291?
CVE-2025-40291 is a high-severity 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:
io_uring: fix regbuf vector size truncation
There is a report of io_estimate_bvec_size() truncating the calculated number of segments that leads to corruption issues. Check it doesn't overflow "int"s used later. Rough but simple, can be improved on top.
Which versions are affected by CVE-2025-40291?
How do I fix CVE-2025-40291?
Apply the vendor's patch.
Is CVE-2025-40291 being exploited?
There is no known exploitation of CVE-2025-40291 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40291, DEBIAN-CVE-2025-40291, GHSA-hcjg-xhvj-4968, UBUNTU-CVE-2025-40291.