# CVE-2026-43133: KVM: nSVM: Always use vmcb01 in VMLOAD/VMSAVE emulation

> A flaw in KVM nSVM emulation allows L2 guests to bypass isolation, potentially leading to privilege escalation or code execution on the host.

- **Severity:** High 7.9 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/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:** 6 May 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-43133, DEBIAN-CVE-2026-43133, GHSA-g9j5-v9rr-m845, ROOT-OS-UBUNTU-2204-CVE-2026-43133, ROOT-OS-UBUNTU-2404-CVE-2026-43133, UBUNTU-CVE-2026-43133

## What is CVE-2026-43133?

CVE-2026-43133 is a high-severity vulnerability in Linux kernel, published on 6 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: nSVM: Always use vmcb01 in VMLOAD/VMSAVE emulation

Commit cc3ed80ae69f ("KVM: nSVM: always use vmcb01 to for vmsave/vmload
of guest state") made KVM always use vmcb01 for the fields controlled by
VMSAVE/VMLOAD, but it missed updating the VMLOAD/VMSAVE emulation code
to always use vmcb01.

As a result, if VMSAVE/VMLOAD is executed by an L2 guest and is not
intercepted by L1, KVM will mistakenly use vmcb02. Always use vmcb01
instead of the current VMCB.

Weakness: CWE-628 (Function Call with Incorrectly Specified Arguments), CWE-754 (Improper Check for Unusual or Exceptional Conditions)

## Which versions are affected by CVE-2026-43133?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43133?

Apply the vendor's patch.

## Is CVE-2026-43133 being exploited?

There is no known exploitation of CVE-2026-43133 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-2026-43133 and fix it if it is affected.

What it is: CVE-2026-43133 is a high-severity vulnerability in Linux kernel, published on 6 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-2026-43133 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-2026-43133/ (Markdown: https://insights.sbomify.com/CVE-2026-43133/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43133
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43133
- OSV: https://osv.dev/vulnerability/CVE-2026-43133

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43133/
Summaries are generated and may contain mistakes; the official description above is the record.