CVE-2021-28694

Guest privilege escalation via replaceable IOMMU identity mappings

Published Aug 27, 2021 · Updated Aug 3, 2024

IOMMU mapping errors in Xen Hypervisor allow guest OS users to escalate privileges, leak information, or interrupt the host. Xen permits a guest to remove or replace firmware-declared identity mappings for untranslated memory regions instead of preserving them. Exploitation requires an x86 host with an IOMMU, relevant ACPI identity-mapped regions, and PCI passthrough to the guest; the outcome is system-specific.

CVSS severity6.8
Medium
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

IOMMU mapping errors in Xen Hypervisor allow guest OS users to escalate privileges, leak information, or interrupt the host. Xen permits a guest to remove or replace firmware-declared identity mappings for untranslated memory regions instead of preserving them. Exploitation requires an x86 host with an IOMMU, relevant ACPI identity-mapped regions, and PCI passthrough to the guest; the outcome is system-specific.

The record

CVE
CVE-2021-28694
Published
Aug 27, 2021
Updated
Aug 3, 2024
Vendor
Xen Project
Product
Xen Hypervisor
Classifications
T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 27, 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=4.11.x
  2. Affected versionversion=4.12.x
  3. Affected versionversion=4.13.x
  4. Affected versionversion=4.14.x
  5. Affected versionversion=4.15.x
  6. Affected versionversion=xen-unstable

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Xen Project · Xen Hypervisorversion=4.11.x; version=4.12.x; version=4.13.x; version=4.14.x; version=4.15.x; version=xen-unstable

Published CVSS scores

6.8NISTAV:L/AC:L/Au:N/C:P/I:P/A:P
6.8NISTCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1068Exploitation for Privilege Escalation

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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