CVE-2023-34327

Guest crash via asymmetric debug-mask context switching

Published Jan 5, 2024 · Updated Nov 4, 2025

Denial of service in Xen 4.5 and later allows guest OS users to crash an unrelated HVM guest through inherited debug-mask state. The SVM context-switch path handles AMD DR_MASK state asymmetrically, so an HVM vCPU can inherit the previous vCPU's mask. Exposure requires AMD or Hygon DBEXT-capable hardware; ordinary debug-mask use by any PV or HVM guest can disrupt another HVM guest.

CVSS severity5.5
Medium
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Xen 4.5 and later allows guest OS users to crash an unrelated HVM guest through inherited debug-mask state. The SVM context-switch path handles AMD DR_MASK state asymmetrically, so an HVM vCPU can inherit the previous vCPU's mask. Exposure requires AMD or Hygon DBEXT-capable hardware; ordinary debug-mask use by any PV or HVM guest can disrupt another HVM guest.

The record

CVE
CVE-2023-34327
Published
Jan 5, 2024
Updated
Nov 4, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 5, 2024CVE publishedPublication date reported by the CVE source.
  2. Nov 4, 2025Record 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 privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.5CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.7SUSECVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/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.

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

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

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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