CVE-2023-34328

x86/AMD: Debug Mask handling

Published Jan 5, 2024 CVSS 3.1 · 5.5 Medium EPSS < 1% KEV · Not listed
Description

[This CNA information record relates to multiple CVEs; the
text explains which aspects/vulnerabilities correspond to which CVE.]

AMD CPUs since ~2014 have extensions to normal x86 debugging functionality.
Xen supports guests using these extensions.

Unfortunately there are errors in Xen's handling of the guest state, leading
to denials of service.

1) CVE-2023-34327 - An HVM vCPU can end up operating in the context of
a previous vCPUs debug mask state.

2) CVE-2023-34328 - A PV vCPU can place a breakpoint over the live GDT.
This allows the PV vCPU to exploit XSA-156 / CVE-2015-8104 and lock
up the CPU entirely.

Remediation

Vendor Workaround

For CVE-2023-34327, HVM VMs which can see the DBEXT feature are not susceptible to running in the wrong state. By default, VMs will see the DBEXT feature on capable hardware, and when not explicitly levelled for migration compatibility. For CVE-2023-34328, PV VMs which cannot see the DBEXT feature cannot leverage the vulnerability.

Tracking

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Advisories

Source ID Title
EUVD EUVD EUVD-2023-38409 [This CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] AMD CPUs since ~2014 have extensions to normal x86 debugging functionality. Xen supports guests using these extensions. Unfortunately there are errors in Xen's handling of the guest state, leading to denials of service. 1) CVE-2023-34327 - An HVM vCPU can end up operating in the context of a previous vCPUs debug mask state. 2) CVE-2023-34328 - A PV vCPU can place a breakpoint over the live GDT. This allows the PV vCPU to exploit XSA-156 / CVE-2015-8104 and lock up the CPU entirely.
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
XEN
Published
Updated
Nov 4, 2025, 7:16 PM
Reserved
Jun 1, 2023, 10:44 AM
Status
Modified
Published
Jan 5, 2024, 5:15 PM
Modified
Jun 17, 2026, 6:03 AM