# CVE-2026-43483: KVM: SVM: Set/clear CR8 write interception when AVIC is (de)activated

> A flaw in Linux KVM SVM implementation causes Windows guests to crash due to TPR synchronization issues when AVIC is activated.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/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:** 13 May 2026
- **Updated:** 13 May 2026
- **Also known as:** BELL-CVE-2026-43483, DEBIAN-CVE-2026-43483, GHSA-8rg3-3364-c6fh, ROOT-OS-DEBIAN-11-CVE-2026-43483, ROOT-OS-UBUNTU-2204-CVE-2026-43483, ROOT-OS-UBUNTU-2404-CVE-2026-43483, UBUNTU-CVE-2026-43483

## What is CVE-2026-43483?

CVE-2026-43483 is a medium-severity denial of service vulnerability in Linux kernel, published on 13 May 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: SVM: Set/clear CR8 write interception when AVIC is (de)activated

Explicitly set/clear CR8 write interception when AVIC is (de)activated to
fix a bug where KVM leaves the interception enabled after AVIC is
activated.  E.g. if KVM emulates INIT=>WFS while AVIC is deactivated, CR8
will remain intercepted in perpetuity.

On its own, the dangling CR8 intercept is "just" a performance issue, but
combined with the TPR sync bug fixed by commit d02e48830e3f ("KVM: SVM:
Sync TPR from LAPIC into VMCB::V_TPR even if AVIC is active"), the danging
intercept is fatal to Windows guests as the TPR seen by hardware gets
wildly out of sync with reality.

Note, VMX isn't affected by the bug as TPR_THRESHOLD is explicitly ignored
when Virtual Interrupt Delivery is enabled, i.e. when APICv is active in
KVM's world.  I.e. there's no need to trigger update_cr8_intercept(), this
is firmly an SVM implementation flaw/detail.

WARN if KVM gets a CR8 write #VMEXIT while AVIC is active, as KVM should
never enter the guest with AVIC enabled and CR8 writes intercepted.

[Squash fix to avic_deactivate_vmcb. - Paolo]

## Which versions are affected by CVE-2026-43483?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43483?

Apply the vendor's patch.

## Is CVE-2026-43483 being exploited?

There is no known exploitation of CVE-2026-43483 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-2026-43483 and fix it if it is affected.

What it is: CVE-2026-43483 is a medium-severity denial of service vulnerability in Linux kernel, published on 13 May 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-2026-43483 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-2026-43483/ (Markdown: https://insights.sbomify.com/CVE-2026-43483/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43483
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43483
- OSV: https://osv.dev/vulnerability/CVE-2026-43483

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43483/
Summaries are generated and may contain mistakes; the official description above is the record.