CVE-2021-28702

Host memory corruption via stale IOMMU mappings

Published Oct 6, 2021 · Updated Aug 3, 2024

IOMMU teardown in Xen Hypervisor 4.13.4, 4.14.3, and 4.15.1 allows attackers to corrupt host memory through PCI DMA. On guest shutdown, Xen fails to deassign an RMRR-using passthrough device, leaving its IOMMU page-table pointers aimed at freed structures. Administrative control of such a guest on an Intel x86 host is required; later DMA or interrupts can cause IOMMU faults, host disruption, memory corruption, or privilege escalation.

CVSS severity7.6
High
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

IOMMU teardown in Xen Hypervisor 4.13.4, 4.14.3, and 4.15.1 allows attackers to corrupt host memory through PCI DMA. On guest shutdown, Xen fails to deassign an RMRR-using passthrough device, leaving its IOMMU page-table pointers aimed at freed structures. Administrative control of such a guest on an Intel x86 host is required; later DMA or interrupts can cause IOMMU faults, host disruption, memory corruption, or privilege escalation.

The record

CVE
CVE-2021-28702
Published
Oct 6, 2021
Updated
Aug 3, 2024
Vendor
Xen Project
Product
Xen Hypervisor
Classifications
T1499.004
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Oct 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.12.x <unspecified

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

Xen Project · Xen Hypervisorversion=4.12.x <unspecified

Published CVSS scores

4.6NVDAV:L/AC:L/Au:N/C:P/I:P/A:P
7.6NVDCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
6.8SUSECVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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