CVE-2025-40216 io_uring/rsrc: don't rely on user vaddr alignment
A logic error in Linux kernel io_uring resource handling incorrectly assumes user pointer alignment, potentially causing memory access issues.
- 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-2025-40216?
CVE-2025-40216 is a high-severity vulnerability in Linux, published on 4 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/rsrc: don't rely on user vaddr alignment
There is no guaranteed alignment for user pointers, however the calculation of an offset of the first page into a folio after coalescing uses some weird bit mask logic, get rid of it.
Which versions are affected by CVE-2025-40216?
How do I fix CVE-2025-40216?
Apply the vendor's patch.
Is CVE-2025-40216 being exploited?
There is no known exploitation of CVE-2025-40216 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40216, DEBIAN-CVE-2025-40216, GHSA-vv4p-ph8q-2hhx, UBUNTU-CVE-2025-40216.