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Epyc 7003 FirmwareOperating system · Amd

CVE-2021-26355

MEDIUM · 5.5 CVSS v3.1 Published 2023-01-11
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
57/100
Remediation priority · Elevated
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Insufficient fencing and checks in System Management Unit (SMU) may result in access to invalid message port registers that could result in a potential denial-of-service.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Insufficient fencing and validation checks in AMD's System Management Unit (SMU) firmware could allow access to invalid message port registers, potentially causing a denial-of-service condition. This is a hardware/firmware-level issue in AMD processors affecting SMU message handling.

MitigationApply AMD-provided firmware/microcode updates for affected processors; check with OEM for BIOS/UEFI updates containing the SMU fix.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Epyc 7003 FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7
Epyc 72f3 FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7
Epyc 7313 FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7
Epyc 7313p FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7
Epyc 7343 FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7
Epyc 7373x FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7
Epyc 73f3 FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7
Epyc 7413 FirmwareOperating system
Affected:< milanpi-sp3_1.0.0.7

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify AMD Epyc processor model
    Run `lscpu | grep -i 'Model name'` or `dmidecode -t processor | grep -i 'AMD Epyc'` to confirm the processor is an AMD Epyc 7003 series (Milan) model such as 72f3, 7313, 7313p, 7343, 7373x, 73f3, or 7413
    Affected if The processor model is one of the listed Epyc 7003 variants and is NOT patched to the latest BIOS/firmware
  2. Check BIOS/UEFI version
    Run `dmidecode -s bios-version` or check the BIOS setup information screen for the firmware version string
    Affected if The BIOS version is dated before the AMD-provided fix containing SMU firmware milanpi-sp3_1.0.0.7 or later
  3. Check SMU firmware version via IPMI
    Run `ipmitool raw` commands or use `ipmitool -I open mc info` to retrieve the BMC firmware version, then cross-reference with AMD's advisory for the SMU firmware component version if exposed
    Affected if The system SMU firmware version is exposed and is earlier than milanpi-sp3_1.0.0.7
  4. Check system firmware update status
    Run `fwupdmgr get-devices` (if fwupd is available) or check with the OEM/hosting provider for the applied BIOS/UEFI update level
    Affected if The installed firmware is not updated to the version containing the SMU fix for CVE-2021-26355
  5. Verify SMU message handling is in use
    This is a passive flaw in SMU firmware; the vulnerability exists regardless of active use if the SMU is running (which it always is on affected processors)
    Affected if The processor is an affected Epyc 7003 model with firmware below the fixed version

The system is affected if it runs an AMD Epyc 7003 series processor with SMU firmware version earlier than milanpi-sp3_1.0.0.7 and the BIOS/firmware has not been patched.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply AMD-provided firmware/microcode updates for affected processors; check with OEM for BIOS/UEFI updates containing the SMU fix.

Recommended fix Moderate confidence

milanpi-sp3_1.0.0.7 or later

  1. 1. Identify the exact AMD Epyc 7003 series processor model(s) in your environment that require the firmware update
  2. 2. Download the latest System Management Unit (SMU) firmware for your specific Epyc processor from the official AMD website (www.amd.com)
  3. 3. Ensure you have a valid backup of the current system configuration and that you have tested the firmware update in a non-production environment first
  4. 4. Apply the firmware update using the appropriate AMD-provided tool or through your system's BIOS/UEFI update mechanism
  5. 5. Verify the firmware version has been successfully updated to milanpi-sp3_1.0.0.7 or later using system information utilities
  6. 6. Reboot the system to ensure the new SMU firmware is properly initialized
  7. 7. Confirm the vulnerability is remediated by checking that the SMU no longer allows access to invalid message port registers
Caveat Firmware updates carry inherent risks; ensure proper backup and testing in non-production environment before deploying to production systems

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Epyc 7003 Firmware Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $890
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-26355 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data