# GSD-2021-1000396: KVM: x86/mmu: Alloc page for PDPTEs when shadowing 32-bit NPT with 64-bit

> A memory corruption flaw in KVM's MMU allows local attackers to escalate privileges or cause denial of service.

- **Severity:** Not scored
- **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:** No
- **Published:** 31 May 2021

## What is GSD-2021-1000396?

GSD-2021-1000396 is a memory corruption vulnerability in Kernel, published on 31 May 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

KVM: x86/mmu: Alloc page for PDPTEs when shadowing 32-bit NPT with 64-bit

This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven.
This ID is fixed in Linux Kernel version v5.10.37 by commit c8b49e01a23b0f5a97dc977812adaf042b474eb7, it was introduced in version v4.19 by commit ee6268ba3a6861b2806e569bff7fe91fbdf846dd. For more details please see the references link.

## Which versions are affected by GSD-2021-1000396?

1 open source package ship an affected version, including Kernel.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `Kernel` | Linux | All versions | None |

## How do I fix GSD-2021-1000396?

No fix has been published for GSD-2021-1000396 yet. Limit exposure of the affected software until one is available.

## Is GSD-2021-1000396 being exploited?

There is no known exploitation of GSD-2021-1000396 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GSD-2021-1000396 and fix it if it is affected.

What it is: GSD-2021-1000396 is a memory corruption vulnerability in Kernel, published on 31 May 2021. 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 GSD-2021-1000396 in the wild and no public exploit code.

Affected packages and fixed versions:
- Kernel (Linux): affected all versions; no fix listed

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/GSD-2021-1000396/ (Markdown: https://insights.sbomify.com/GSD-2021-1000396/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GSD-2021-1000396

---
From sbomify Insights: https://insights.sbomify.com/GSD-2021-1000396/
Summaries are generated and may contain mistakes; the official description above is the record.