CVE-2021-26326

Memory integrity loss via unchecked VM_HSAVE_PA initialization

Published Nov 16, 2021 · Updated Sep 16, 2024

Improper initialization in AMD 3rd Gen EPYC firmware before MilanPI-SP3_1.0.0.4 allows local users to compromise memory integrity. During SNP_INIT, the firmware fails to verify that the VM_HSAVE_PA model-specific register is zero across all cores before establishing Secure Nested Paging state. The path requires local access to the affected SEV-SNP platform; successful exploitation permits unauthorized modification of protected memory.

CVSS severity7.8
High
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

Improper initialization in AMD 3rd Gen EPYC firmware before MilanPI-SP3_1.0.0.4 allows local users to compromise memory integrity. During SNP_INIT, the firmware fails to verify that the VM_HSAVE_PA model-specific register is zero across all cores before establishing Secure Nested Paging state. The path requires local access to the affected SEV-SNP platform; successful exploitation permits unauthorized modification of protected memory.

The record

CVE
CVE-2021-26326
Published
Nov 16, 2021
Updated
Sep 16, 2024
Vendor
Advanced Micro Devices, Inc.
Product
3rd Gen AMD EPYC Processors
Classifications
CWE-665
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 16, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 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=unspecified <MilanPI-SP3_1.0.0.4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Advanced Micro Devices, Inc. · 3rd Gen AMD EPYC Processorsversion=unspecified <MilanPI-SP3_1.0.0.4

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.2NIST NVDAV:L/AC:L/Au:N/C:C/I:C/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-665Improper Initialization

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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