CVE-2021-26404

Local information disclosure via SEV scratch-buffer leakage

Published Jan 10, 2023 · Updated Apr 8, 2025

Improper input validation in SEV-SNP firmware on 3rd Gen AMD EPYC processors allows local users to read scratch-buffer bytes. The SEV firmware applies inadequate input validation and bounds checks, causing scratch-buffer contents to be included in an observable result. Exploitation requires local low-privileged access to an SEV-SNP host and affects confidentiality without altering data or interrupting service.

CVSS severity5.5
Medium
EPSS probability0.18%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in SEV-SNP firmware on 3rd Gen AMD EPYC processors allows local users to read scratch-buffer bytes. The SEV firmware applies inadequate input validation and bounds checks, causing scratch-buffer contents to be included in an observable result. Exploitation requires local low-privileged access to an SEV-SNP host and affects confidentiality without altering data or interrupting service.

The record

CVE
CVE-2021-26404
Published
Jan 10, 2023
Updated
Apr 8, 2025
Vendor
Advanced Micro Devices, Inc.
Product
3rd Gen AMD EPYC Processors
Classifications
CWE-20, T1005
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 10, 2023CVE publishedPublication date reported by the CVE source.
  2. Apr 8, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=various

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Advanced Micro Devices, Inc. · 3rd Gen AMD EPYC Processorsversion=various

Published CVSS scores

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

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-20Improper Input Validation
T1005Data from Local System

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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