# CVE-2026-98164: KVM: x86/mmu: Check write tracking in all address spaces

> A logic error in KVM's write tracking allows triggering a kernel BUG, causing a denial of service.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/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:** 29 Sep 2026
- **Updated:** 7 Oct 2026
- **Also known as:** BELL-CVE-2026-98164, DEBIAN-CVE-2026-98164, GHSA-4wvx-xqjp-p7g6, UBUNTU-CVE-2026-98164

## What is CVE-2026-98164?

CVE-2026-98164 is a high-severity memory corruption vulnerability in Linux kernel, published on 29 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: x86/mmu: Check write tracking in all address spaces

kvm_gfn_is_write_tracked() checks only the supplied memslot, but page
tracking is per-address-space and shadow pages are shared across all
address spaces.  With SMM, a GFN can therefore be write-tracked in one
address space and appear untracked through the other.

Check the supplied slot first, then the slot for the other address space.
This ensures all callers honor write tracking regardless of the active
address space.  In particular, it prevents mmu_try_to_unsync_pages() from
marking an upper-level shadow page unsync and eventually triggering the
BUG in pte_list_remove().

[invert direction of the conditional. - Paolo]

Weakness: CWE-670 (Always-Incorrect Control Flow Implementation)

## Which versions are affected by CVE-2026-98164?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-98164?

Apply the vendor's patch.

## Is CVE-2026-98164 being exploited?

There is no known exploitation of CVE-2026-98164 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98164 and fix it if it is affected.

What it is: CVE-2026-98164 is a high-severity memory corruption vulnerability in Linux kernel, published on 29 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-2026-98164 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-98164/ (Markdown: https://insights.sbomify.com/CVE-2026-98164/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98164
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98164
- OSV: https://osv.dev/vulnerability/CVE-2026-98164

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98164/
Summaries are generated and may contain mistakes; the official description above is the record.