# CVE-2026-89929: KVM: nVM: Ensure INVVPID is emulated on the correct physical CPU

> A race condition in KVM nested virtualization allows stale TLB entries, potentially enabling data leakage or privilege escalation.

- **Severity:** High 8.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/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:** 16 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-101277, BELL-CVE-2026-89929, DEBIAN-CVE-2026-89929, GHSA-78pj-hm8w-chf6, UBUNTU-CVE-2026-89929

## What is CVE-2026-89929?

CVE-2026-89929 is a high-severity vulnerability in Linux, published on 16 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: nVM: Ensure INVVPID is emulated on the correct physical CPU

When emulating INVVPID, KVM executes INVVPID on the physical CPU using
vpid02 (instead of the L1 assigned VPID), after doing some validations
on the operands. However, it is possible that the physical CPU KVM
executes INVVPID on is different from the CPU L2 is running on.

For example, in the following scenario:
- L2 runs on CPU #1 and exits to L1 (vmx->nested.vmcs02.cpu=1)
- L1 migrates to CPU #2 and executes INVVPID
- KVM executes INVVPID on CPU #2
- L1 migrates back to CPU #1 and runs L2 (vmx->nested.vmcs02.cpu=1)

The TLB entries on CPU #1 are never invalidated, because INVVPID was
executed on CPU #2, and vmcs02 never ran on a different pCPU (i.e.
vmx_vcpu_load_vmcs() will *not* request KVM_REQ_TLB_FLUSH).

Ensure that INVVPID is being executed on the same pCPU that L2 last ran
on, and if not, fallback to clearing last_vpid=0 to trigger a full VPID
flush on the next nested VM-Enter (as KVM will detect L1 using a
different VPID for L2). If L2 ends up running on a different pCPU, KVM
will flush the TLB anyway through vmx_vcpu_load_vmcs().

## Which versions are affected by CVE-2026-89929?


## How do I fix CVE-2026-89929?

Apply the vendor's patch.

## Is CVE-2026-89929 being exploited?

There is no known exploitation of CVE-2026-89929 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89929 and fix it if it is affected.

What it is: CVE-2026-89929 is a high-severity vulnerability in Linux, published on 16 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-2026-89929 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-2026-89929/ (Markdown: https://insights.sbomify.com/CVE-2026-89929/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89929
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89929
- OSV: https://osv.dev/vulnerability/CVE-2026-89929

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89929/
Summaries are generated and may contain mistakes; the official description above is the record.