CVE-2026-89568 kho: fix size calculation in kho_preserved_memory_reserve()
A local attacker with high privileges can trigger undefined behavior and potential denial of service by requesting memory reservations larger than 2 GiB due to an integer overflow in size calculation.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89568?
CVE-2026-89568 is a vulnerability in Linux, published on 11 Sep 2026. 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:
kho: fix size calculation in kho_preserved_memory_reserve()
kho_preserved_memory_reserve() calculates the size of a preservation by doing 1 << (order + PAGE_SHIFT). Since the '1' is a 32-bit integer, it can only be shifted by 31. That is, it will only work for preservations up to 2 GiB. Larger preservations will trigger undefined behaviour.
While preservations larger than 2 GiB can't be obtained via folios currently, they can be obtained via kho_preserve_pages().
For example, memblock reserve_mem uses kho_preserve_pages(). Reservations larger than 2 GiB are valid and will trigger this bug if properly aligned.
Fix it by using 1UL for shifting.
Which versions are affected by CVE-2026-89568?
How do I fix CVE-2026-89568?
Apply the vendor's patch.
Is CVE-2026-89568 being exploited?
There is no known exploitation of CVE-2026-89568 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-89568, DEBIAN-CVE-2026-89568, GHSA-832m-273v-9hpc, UBUNTU-CVE-2026-89568.