CVE-2026-89959 s390/vfio-ap: Fix control domain removal in vfio_ap_mdev_cfg_remove
Incorrect bitmap operation in the Linux kernel s390 vfio-ap driver prevents proper removal of control domains from KVM guests.
- 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-2026-89959?
CVE-2026-89959 is a high-severity vulnerability in Linux, published on 16 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:
s390/vfio-ap: Fix control domain removal in vfio_ap_mdev_cfg_remove
The vfio_ap_config_remove function uses the bitmap_andnot function to clear bits from the matrix_mdev->matrix.adm bitmap (specifies the control domains assigned to the mdev). This prevents the explicitly unplugged control domains from being removed the KVM guest. The bitmap_and function is used instead.
Which versions are affected by CVE-2026-89959?
How do I fix CVE-2026-89959?
Apply the vendor's patch.
Is CVE-2026-89959 being exploited?
There is no known exploitation of CVE-2026-89959 in the wild and no public exploit code.
Sources
Also known as AZL-101180, BELL-CVE-2026-89959, DEBIAN-CVE-2026-89959, GHSA-8mfq-hrvh-mwqh, UBUNTU-CVE-2026-89959.