CVE-2021-26355

Service interruption via invalid SMU register access

Published Jan 10, 2023 · Updated Apr 9, 2025

Denial of service in the AMD EPYC 7003 System Management Unit allows local users to interrupt service through invalid register access. Insufficient fencing and validation permit the SMU to access invalid message-port registers. Low-privileged local access is required, and AMD does not specify whether the interruption is a hang, crash, reboot, or shutdown.

CVSS severity5.5
Medium
EPSS probability0.17%
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 the AMD EPYC 7003 System Management Unit allows local users to interrupt service through invalid register access. Insufficient fencing and validation permit the SMU to access invalid message-port registers. Low-privileged local access is required, and AMD does not specify whether the interruption is a hang, crash, reboot, or shutdown.

The record

CVE
CVE-2021-26355
Published
Jan 10, 2023
Updated
Apr 9, 2025
Vendor
Advanced Micro Devices, Inc.
Product
3rd Gen AMD EPYC Processors
Classifications
CWE-693, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 10, 2023CVE publishedPublication date reported by the CVE source.
  2. Apr 9, 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:N/I:N/A:H
5.5CISA-ADPCVSS: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.

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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-693Protection Mechanism Failure
T1499.004Application or System Exploitation

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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