# CVE-2021-47035: iommu/vt-d: Remove WO permissions on second-level paging entries

> The Linux kernel allowed unsupported Write-Only permissions in IOMMU second-level paging, potentially bypassing intended read restrictions.

- **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:** 28 Feb 2024
- **Updated:** 5 Aug 2026
- **Also known as:** DEBIAN-CVE-2021-47035, GHSA-qp35-683c-hfxv, UBUNTU-CVE-2021-47035

## What is CVE-2021-47035?

CVE-2021-47035 is a high-severity vulnerability in Linux kernel, published on 28 Feb 2024. 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:

iommu/vt-d: Remove WO permissions on second-level paging entries

When the first level page table is used for IOVA translation, it only
supports Read-Only and Read-Write permissions. The Write-Only permission
is not supported as the PRESENT bit (implying Read permission) should
always set. When using second level, we still give separate permissions
that allows WriteOnly which seems inconsistent and awkward. We want to
have consistent behavior. After moving to 1st level, we don't want things
to work sometimes, and break if we use 2nd level for the same mappings.
Hence remove this configuration.

## Which versions are affected by CVE-2021-47035?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47035?

Apply the vendor's patch.

## Is CVE-2021-47035 being exploited?

There is no known exploitation of CVE-2021-47035 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-2021-47035 and fix it if it is affected.

What it is: CVE-2021-47035 is a high-severity vulnerability in Linux kernel, published on 28 Feb 2024. 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-2021-47035 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-2021-47035/ (Markdown: https://insights.sbomify.com/CVE-2021-47035/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47035
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47035
- OSV: https://osv.dev/vulnerability/CVE-2021-47035

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47035/
Summaries are generated and may contain mistakes; the official description above is the record.