CVE-2026-89916 KVM: arm64: Make VNCR invalidation participate in MMU invalidation retry
A race condition in KVM arm64 VNCR invalidation allows attackers to execute arbitrary code or escalate privileges within the guest.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89916?
CVE-2026-89916 is a critical 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:
KVM: arm64: Make VNCR invalidation participate in MMU invalidation retry
A VNCR TLB invalidation can occur on one vcpu while another vcpu is faulting in this same page. Without correctly handling this, we can end up with the following scenario:
- vcpu A walks the PTs to translate VNCR - before vcpu A is able to grab the MMU lock to insert the TLB, vcpu B updates the S1 PTs with an invalid entry, and issues a TLBI S1E2 for this VA - vcpu A inserts the TLB for something that is now invalid
This isn't a new problem, and we manage S2 by having the MMU notifier to bump up mmu_invalidate_seq on invalidation so that the fault can be replayed.
We can perform something similar here, and extend invalidate_vncr_va() to update the same counter, clearly indicating that the context has changed under our feet. This is safe as the invalidation always happen while holding the MMU lock for write, and that we sample the sequence number before walking S1.
Which versions are affected by CVE-2026-89916?
How do I fix CVE-2026-89916?
Apply the vendor's patch.
Is CVE-2026-89916 being exploited?
There is no known exploitation of CVE-2026-89916 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-89916, DEBIAN-CVE-2026-89916, GHSA-5p99-rg43-px7f, UBUNTU-CVE-2026-89916.