CVE-2026-89593 hugetlb: only adjust reservation during unmapping if mapcount is 0
A logic error in Linux kernel hugetlb unmapping causes reservation count underflow, potentially leading to 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-2026-89593?
CVE-2026-89593 is a high-severity 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:
hugetlb: only adjust reservation during unmapping if mapcount is 0
Since df7a6d1f6405, __unmap_hugepage_range can adjust reservations. In the case of folio mapped in both a parent and a child, if the parent unmaps the range first, the reservation adjustment will result in an underflow of the reserved count. Once the child unmaps the range, the count is restored. Change __unmap_hugepage_range() to check the mapcount before adjusting the reservation.
Which versions are affected by CVE-2026-89593?
How do I fix CVE-2026-89593?
Apply the vendor's patch.
Is CVE-2026-89593 being exploited?
There is no known exploitation of CVE-2026-89593 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-89593, DEBIAN-CVE-2026-89593, GHSA-xm38-wfrw-x5q7, UBUNTU-CVE-2026-89593.