# CVE-2026-99168: mshv_vtl: Check per-CPU register page before mmap


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-99168, GHSA-3wc5-v6vv-97qx, UBUNTU-CVE-2026-99168

## What is CVE-2026-99168?

CVE-2026-99168 is a vulnerability in Linux, published on 28 Oct 2026. 

### Official description

In the Linux kernel, the following vulnerability has been resolved:

mshv_vtl: Check per-CPU register page before mmap

Register-page setup is optional for each CPU. If allocation or
registration fails, mshv_vtl_configure_reg_page() warns and leaves that
CPU's reg_page NULL, but initial context setup continues successfully.
Meanwhile, successful setup on another CPU sets the global
mshv_has_reg_page flag.

mshv_vtl_fault() checks this global flag before selecting the requested
CPU's register page. With mixed setup results across online CPUs, the
check passes even for a CPU with no register page, reaching
get_page(NULL) when userspace faults in that mapping.

Check the selected per-CPU register page before taking its reference and
return VM_FAULT_SIGBUS if it is absent.

## Which versions are affected by CVE-2026-99168?


## How do I fix CVE-2026-99168?

Upgrade to a fixed version.

## Is CVE-2026-99168 being exploited?

There is no known exploitation of CVE-2026-99168 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99168 and fix it if it is affected.

What it is: CVE-2026-99168 is a vulnerability in Linux, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99168 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-2026-99168/ (Markdown: https://insights.sbomify.com/CVE-2026-99168/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99168
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99168
- OSV: https://osv.dev/vulnerability/CVE-2026-99168

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99168/
Summaries are generated and may contain mistakes; the official description above is the record.