CVE-2026-45251 Kernel use-after-free via file descriptor syscalls
An unprivileged local user can exploit a use-after-free in the FreeBSD kernel to gain superuser privileges.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-45251?
CVE-2026-45251 is a high-severity use after free vulnerability in Freebsd Freebsd, published on 21 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
A file descriptor can be closed while a thread is blocked in a poll(2) or select(2) call waiting for that descriptor. Because the blocked thread does not hold a reference to the underlying object, this closure may result in the object being freed while the thread remains blocked. In this situation, the kernel must remove the blocked thread from the per-object wait queue prior to freeing the object.
In the case of some file descriptor types, the kernel failed to unlink blocked threads from the object before freeing it. When the blocked thread is subsequently woken, it accesses memory that has already been freed resulting in a use-after-free vulnerability.
The use-after-free vulnerability may be triggered by an unprivileged local user and can be exploited to obtain superuser privileges.
Weakness: CWE-416
Which versions are affected by CVE-2026-45251?
It affects 1 product.
Products include Freebsd Freebsd.
How do I fix CVE-2026-45251?
No fix has been published for CVE-2026-45251 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-45251 being exploited?
There is no known exploitation of CVE-2026-45251 in the wild and no public exploit code.
Other vulnerabilities in Freebsd Freebsd
Sources
Also known as GHSA-wp9w-fp98-2cxm.