# 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.

- **Severity:** Critical 9.3 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-89918, DEBIAN-CVE-2026-89918, GHSA-hcq6-hvjh-vf66, UBUNTU-CVE-2026-89918

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89918 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-89918 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-89918/ (Markdown: https://insights.sbomify.com/CVE-2026-89918/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89918
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89918
- OSV: https://osv.dev/vulnerability/CVE-2026-89918

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89918/
Summaries are generated and may contain mistakes; the official description above is the record.