CVE-2021-26350

Service interruption via SMU message-port address race

Published May 11, 2022 · Updated Sep 16, 2024

A TOCTOU race condition in the AMD EPYC SMU allows local users to interrupt service by manipulating a message port register address. The SMU permits the caller to obtain and alter that register address between the check and subsequent use, so the operation targets a changed address. Low-privileged local access and winning the race are required; AMD reports denial of service but does not identify whether the system hangs, crashes, or reboots.

CVSS severity4.7
Medium
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A TOCTOU race condition in the AMD EPYC SMU allows local users to interrupt service by manipulating a message port register address. The SMU permits the caller to obtain and alter that register address between the check and subsequent use, so the operation targets a changed address. Low-privileged local access and winning the race are required; AMD reports denial of service but does not identify whether the system hangs, crashes, or reboots.

The record

CVE
CVE-2021-26350
Published
May 11, 2022
Updated
Sep 16, 2024
Vendor
AMD
Product
AMD EPYC Processors
Classifications
CWE-367, CAPEC-29, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 11, 2022CVE 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?

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  1. Affected versionversion=various

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

AMD · AMD EPYC Processorsversion=various

Published CVSS scores

4.7NIST NVDCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
1.9NIST NVDAV:L/AC:M/Au:N/C:N/I:N/A:P

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-367Time-of-check Time-of-use (TOCTOU) Race Condition
CAPEC-29Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions
T1499Endpoint Denial of Service

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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