CVE-2021-26331

Local code execution via SMU mailbox manipulation

Published Nov 16, 2021 · Updated Sep 16, 2024

Improper input validation in AMD EPYC System Management Unit firmware allows local users to execute arbitrary code via manipulated mailbox entries. The SMU accepts attacker-controlled mailbox values without sufficient validation, enabling code execution within the processor management component. Exploitation requires local access capable of reaching the mailbox interface; the resulting execution can compromise processor firmware integrity and availability.

CVSS severity7.8
High
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in AMD EPYC System Management Unit firmware allows local users to execute arbitrary code via manipulated mailbox entries. The SMU accepts attacker-controlled mailbox values without sufficient validation, enabling code execution within the processor management component. Exploitation requires local access capable of reaching the mailbox interface; the resulting execution can compromise processor firmware integrity and availability.

The record

CVE
CVE-2021-26331
Published
Nov 16, 2021
Updated
Sep 16, 2024
Vendor
AMD
Product
2nd Gen AMD EPYC Processors
Classifications
CWE-20
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 <RomePI-SP3_1.0.0.C

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

AMD · 2nd Gen AMD EPYC Processorsversion=unspecified <RomePI-SP3_1.0.0.C
AMD · 3rd Gen AMD EPYC Processorsversion=unspecified <MilanPI-SP3_1.0.0.4
AMD · 1st Gen AMD EPYC Processorsversion=unspecified <NaplesPI-SP3_1.0.0.G

Published CVSS scores

7.2NVDAV:L/AC:L/Au:N/C:C/I:C/A:C
7.8NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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 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

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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