CVE-2025-39963 io_uring: fix incorrect io_kiocb reference in io_link_skb
A logic error in the Linux kernel's io_uring subsystem causes incorrect reference handling, potentially leading to memory corruption and 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-2025-39963?
CVE-2025-39963 is a high-severity memory corruption vulnerability in Linux kernel, published on 9 Oct 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 incorrect io_kiocb reference in io_link_skb
In io_link_skb function, there is a bug where prev_notif is incorrectly assigned using 'nd' instead of 'prev_nd'. This causes the context validation check to compare the current notification with itself instead of comparing it with the previous notification.
Fix by using the correct prev_nd parameter when obtaining prev_notif.
Weakness: CWE-401
Which versions are affected by CVE-2025-39963?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-39963?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2025-39963 being exploited?
There is no known exploitation of CVE-2025-39963 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-39963, DEBIAN-CVE-2025-39963, GHSA-w6f6-h6gc-qpjj, ROOT-OS-DEBIAN-13-CVE-2025-39963, UBUNTU-CVE-2025-39963.