# CVE-2026-98440: KVM: arm64: nv: Delay freeing of shadow S2 structures until VM destruction

> A use-after-free vulnerability in the Linux kernel's KVM arm64 nested virtualization allows local attackers to potentially execute code or escalate privileges.

- **Severity:** High 7.0 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** Yes
- **Published:** 18 Oct 2026
- **Updated:** 24 Oct 2026
- **Also known as:** BELL-CVE-2026-98440, DEBIAN-CVE-2026-98440, GHSA-f55r-7vvq-j4jq, UBUNTU-CVE-2026-98440

## What is CVE-2026-98440?

CVE-2026-98440 is a high-severity use after free vulnerability in Linux, published on 18 Oct 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: nv: Delay freeing of shadow S2 structures until VM destruction

We free the shadow S2 structures from kvm_arch_flush_shadow_all(), which
is a Bad Idea(tm). Freeing the page tables is fair game (this is what
this callback is for), but freeing the container that could still be
referenced by another part of the system is not great.

Instead, grow separate destructors that gets called when we tear the VM
down for good. From there, we can nuke both the individual MMUs as well
as the global array that points to them, safe in the knowledge that the
vcpus themselves have been destroyed already.

## Which versions are affected by CVE-2026-98440?


## How do I fix CVE-2026-98440?

Apply the vendor's patch.

## Is CVE-2026-98440 being exploited?

There is no known exploitation of CVE-2026-98440 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98440 and fix it if it is affected.

What it is: CVE-2026-98440 is a high-severity use after free vulnerability in Linux, published on 18 Oct 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-2026-98440 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-2026-98440/ (Markdown: https://insights.sbomify.com/CVE-2026-98440/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98440
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98440
- OSV: https://osv.dev/vulnerability/CVE-2026-98440

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98440/
Summaries are generated and may contain mistakes; the official description above is the record.