# CVE-2026-46076: KVM: nSVM: Raise #UD if unhandled VMMCALL isn't intercepted by L1

> A guest VM can bypass L1 hypervisor controls by executing VMMCALL instructions that are not properly intercepted, potentially violating isolation boundaries.

- **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:** 27 May 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-88614, BELL-CVE-2026-46076, DEBIAN-CVE-2026-46076, GHSA-gj33-hwgc-v3v8, ROOT-OS-UBUNTU-2404-CVE-2026-46076, UBUNTU-CVE-2026-46076

## What is CVE-2026-46076?

CVE-2026-46076 is a high-severity vulnerability in Linux kernel, published on 27 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: Raise #UD if unhandled VMMCALL isn't intercepted by L1

Explicitly synthesize a #UD for VMMCALL if L2 is active, L1 does NOT want
to intercept VMMCALL, nested_svm_l2_tlb_flush_enabled() is true, and the
hypercall is something other than one of the supported Hyper-V hypercalls.
When all of the above conditions are met, KVM will intercept VMMCALL but
never forward it to L1, i.e. will let L2 make hypercalls as if it were L1.

The TLFS says a whole lot of nothing about this scenario, so go with the
architectural behavior, which says that VMMCALL #UDs if it's not
intercepted.

Opportunistically do a 2-for-1 stub trade by stub-ifying the new API
instead of the helpers it uses.  The last remaining "single" stub will
soon be dropped as well.

[sean: rewrite changelog and comment, tag for stable, remove defunct stubs]

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-46076?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-46076?

Apply the vendor's patch.

## Is CVE-2026-46076 being exploited?

There is no known exploitation of CVE-2026-46076 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-2026-46076 and fix it if it is affected.

What it is: CVE-2026-46076 is a high-severity vulnerability in Linux kernel, published on 27 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-2026-46076 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-2026-46076/ (Markdown: https://insights.sbomify.com/CVE-2026-46076/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46076
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46076
- OSV: https://osv.dev/vulnerability/CVE-2026-46076

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46076/
Summaries are generated and may contain mistakes; the official description above is the record.