# CVE-2021-28692: Privilege escalation in xen

> Improper IOMMU timeout handling in Xen allows guest VMs to crash other guests or bypass security checks, leading to privilege escalation or denial of service.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/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:** 30 Jun 2021
- **Updated:** 3 Aug 2024
- **Also known as:** ALPINE-CVE-2021-28692, DEBIAN-CVE-2021-28692, GHSA-23j5-p74r-rvqm, UBUNTU-CVE-2021-28692

## What is CVE-2021-28692?

CVE-2021-28692 is a high-severity vulnerability in Xen Xen, published on 30 Jun 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

Weakness: CWE-269 (Improper Privilege Management)

## Which versions are affected by CVE-2021-28692?

It affects 1 product.


Products: Xen Xen.

## How do I fix CVE-2021-28692?

Apply the vendor's patch.

## Is CVE-2021-28692 being exploited?

There is no known exploitation of CVE-2021-28692 in the wild and no public exploit code.

## Other vulnerabilities in Xen Xen

- [CVE-2017-10912](https://insights.sbomify.com/CVE-2017-10912/): Privilege escalation in n/a (critical 10.0)
- [CVE-2017-10918](https://insights.sbomify.com/CVE-2017-10918/): Memory corruption in n/a (critical 10.0)
- [CVE-2017-10920](https://insights.sbomify.com/CVE-2017-10920/): Memory corruption in n/a (critical 10.0)
- [CVE-2017-10921](https://insights.sbomify.com/CVE-2017-10921/): Memory corruption in n/a (critical 10.0)
- [CVE-2025-27466](https://insights.sbomify.com/CVE-2025-27466/): Mutiple vulnerabilities in the Viridian interface (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-28692 and fix it if it is affected.

What it is: CVE-2021-28692 is a high-severity vulnerability in Xen Xen, published on 30 Jun 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 CVE-2021-28692 in the wild and no public exploit code.

Affected product: Xen Xen. 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-2021-28692/ (Markdown: https://insights.sbomify.com/CVE-2021-28692/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-28692
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-28692
- OSV: https://osv.dev/vulnerability/CVE-2021-28692

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-28692/
Summaries are generated and may contain mistakes; the official description above is the record.