# CVE-2021-27379: Privilege escalation in n/a

> Guest OS users can gain privileges or crash the host via incorrect IOMMU updates due to a missed flush in Xen.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/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:** 18 Feb 2021
- **Updated:** 3 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-27379, GHSA-f444-f4gw-jhg6, SUSE-SU-2021:1250-1, SUSE-SU-2021:1268-1, UBUNTU-CVE-2021-27379

## What is CVE-2021-27379?

CVE-2021-27379 is a high-severity vulnerability in Debian Debian Linux, published on 18 Feb 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An issue was discovered in Xen through 4.11.x, allowing x86 Intel HVM guest OS users to achieve unintended read/write DMA access, and possibly cause a denial of service (host OS crash) or gain privileges. This occurs because a backport missed a flush, and thus IOMMU updates were not always correct. NOTE: this issue exists because of an incomplete fix for CVE-2020-15565.

## Which versions are affected by CVE-2021-27379?

It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `xen` | SUSE:Linux Enterprise High Performance Computing 15-ESPOS | All versions | 4.10.4_24-3.56.1 |
| `xen` | SUSE:Linux Enterprise High Performance Computing 15-LTSS | All versions | 4.10.4_24-3.56.1 |
| `xen` | SUSE:Linux Enterprise Server 12 SP2-BCL | All versions | 4.7.6_14-43.76.1 |
| `xen` | SUSE:Linux Enterprise Server for SAP Applications 15 | All versions | 4.10.4_24-3.56.1 |
| `xen` | SUSE:OpenStack Cloud 7 | All versions | 4.7.6_14-43.76.1 |

Products: Debian Debian Linux, Xen Xen.

## How do I fix CVE-2021-27379?

Apply the vendor's patch.

## Is CVE-2021-27379 being exploited?

There is no known exploitation of CVE-2021-27379 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-27379 and fix it if it is affected.

What it is: CVE-2021-27379 is a high-severity vulnerability in Debian Debian Linux, published on 18 Feb 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-2021-27379 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2021-27379/ (Markdown: https://insights.sbomify.com/CVE-2021-27379/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-27379
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-27379
- OSV: https://osv.dev/vulnerability/CVE-2021-27379

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-27379/
Summaries are generated and may contain mistakes; the official description above is the record.