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NVD / CVE Program· CNA AMD

CVE-2021-26355: Insufficient fencing and checks in System Management Unit (SMU) may result in access to invalid message port registers that could result in

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.17% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • According to the record, no fixed version is available yet.

Low priority for now. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 5.5 · v3.1—No exploit No fix recorded
Published
Jan 11, 2023
Updated
Jun 16, 2026
EPSS
0.1% · 7th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-26355

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
amdepyc 7313
amdepyc 7003 firmware
amdepyc 7003
amdepyc 72f3 firmware
amdepyc 72f3
amdepyc 7313 firmware
amdepyc 7313p firmware
amdepyc 7313p
amdepyc 7343 firmware
amdepyc 7343
amdepyc 7373x firmware
amdepyc 7373x

and 36 more

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • amd epyc 7003 firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 72f3 firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 7313 firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 7313p firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 7343 firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 7373x firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 73f3 firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 7413 firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 7443 firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 7443p firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 7453 firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 74f3 firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 7513 firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 7543 firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 7543p firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 7573x firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 75f3 firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 7643 firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 7663 firmwarebefore milanpi-sp3_1.0.0.7
  • amd epyc 7713 firmwarebefore milanpi-sp3_1.0.0.7

Versions reported by the vendor

Affected version ranges reported by the assigning authority (AMD). Independent of NVD's CPE analysis and usually ahead of it.

  • AMD 3rd Gen EPYC

    • variousaffected

Same product

amd: all records

Other highest-scoring records for the same primary product.

  • CVE-2021-26335Improper input and range checking in the AMD Secure Processor (ASP) boot loader image header may allow an attacker to use attacker-controlle
    31Monitor
  • CVE-2021-26331AMD System Management Unit (SMU) contains a potential issue where a malicious user may be able to manipulate mailbox entries leading to arbi
    31Monitor
  • CVE-2021-26315When the AMD Platform Security Processor (PSP) boot rom loads, authenticates, and subsequently decrypts an encrypted FW, due to insufficient
    31Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2021-26328Jan 11, 2023 · Failure to verify the mode of CPU execution at the time of SNP_INIT may lead to a potential loss of memory integrity for SNP guests.
    17Monitor
  • ← EarlierCVE-2021-26343Jan 11, 2023 · Insufficient validation in ASP BIOS and DRTM commands may allow malicious supervisor x86 software to disclose the contents of sensitive memo
    22Monitor
  • Later →CVE-2021-26396Jan 11, 2023 · Insufficient validation of address mapping to IO in ASP (AMD Secure Processor) may result in a loss of memory integrity in the SNP guest.
    17Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-693 · Protection Mechanism Failure

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records