CVE-2026-89918 KVM: arm64: Correctly handle end of VA space TLBI invalidation
A logic error in KVM arm64 TLB invalidation causes failed invalidations at the end of the VA space, potentially allowing stale TLB entries to persist.
- 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-2026-89918?
CVE-2026-89918 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: Correctly handle end of VA space TLBI invalidation
Our TLB invalidation by VA code is based on comparing two ranges, one defined by the TLB, and one defined by the TLBI instruction.
Each range is defined by a start and a size. However, the way the comparison is done doesn't account for address rollover, as it compares an address with (base + size). This works nicely until this expression represent the last page/block in the TTBR1 VA space, as the result is a big fat 0. And a failed TLB invalidation.
Rewrite the comparison in a way that is immune to the address rollover (making the end address inclusive instead of exclusive), and move this into a common helper that is used by both VA and IPA invalidations, as suggested by Hyunwoo Kim (although the IPA version didn't suffer from this particular problem, obviously).
Which versions are affected by CVE-2026-89918?
How do I fix CVE-2026-89918?
Apply the vendor's patch.
Is CVE-2026-89918 being exploited?
There is no known exploitation of CVE-2026-89918 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-89918, DEBIAN-CVE-2026-89918, GHSA-hcq6-hvjh-vf66, UBUNTU-CVE-2026-89918.