CVE-2021-27379

Guest-to-host privilege escalation via stale DMA mappings

Published Feb 18, 2021 · Updated Aug 3, 2024

IOMMU update errors in Xen Project Xen 3.2 through 4.11 allow guest OS users to retain read/write DMA access to freed host frames. The XSA-321 backport omits an IOMMU flush after page-table changes, leaving stale DMA mappings when Xen returns frames to its free pool. Exploitation requires an Intel x86 HVM guest using hardware-assisted paging, PCI passthrough, and shared page tables; Xen reports host crashes and privilege escalation as possible consequences.

CVSS severity7.8
High
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

IOMMU update errors in Xen Project Xen 3.2 through 4.11 allow guest OS users to retain read/write DMA access to freed host frames. The XSA-321 backport omits an IOMMU flush after page-table changes, leaving stale DMA mappings when Xen returns frames to its free pool. Exploitation requires an Intel x86 HVM guest using hardware-assisted paging, PCI passthrough, and shared page tables; Xen reports host crashes and privilege escalation as possible consequences.

The record

CVE
CVE-2021-27379
Published
Feb 18, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1499.004, T1068
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Feb 18, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.9SUSECVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
5.9NIST NVDAV:L/AC:M/Au:N/C:P/I:P/A:C

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
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation
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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