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

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.

Metrics

CVSS 3.1

7.6/10

CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS Probability

0.43%

34.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-269

Affected Software

Vendor	Product	Versions
Xen	Xen	>= 4.13.0, <= 4.15.1
Fedoraproject	Fedora	33
Fedoraproject	Fedora	34
Fedoraproject	Fedora	35
Debian	Debian Linux	9.0

References

Timeline

Published: Oct 6, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-28702?

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.

How severe is CVE-2021-28702?

CVE-2021-28702 has a CVSS score of 7.6/10 (HIGH severity). The EPSS model estimates a 0.43% probability of exploitation in the next 30 days.

How do I fix CVE-2021-28702?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.