Security readout for executives and security teams
Plain-English summary
This is an AMD 3rd Gen EPYC platform issue that could let a local low-privileged user trigger a denial-of-service condition through the System Management Unit. It does not indicate data theft or remote takeover in the supplied sources.
Executive priority
Handle through normal firmware risk management, with higher priority for shared or multi-tenant servers. Business impact is service disruption, not confirmed data compromise, and evidence of active exploitation is absent in the provided sources.
Technical view
CVE-2021-26355 is a CWE-693 weakness involving insufficient fencing and checks in AMD SMU handling. Access to invalid message port registers may cause denial of service. CVSS 3.1 is 5.5: local access, low complexity, low privileges, no user interaction, availability impact only.
Likely exposure
Likely exposure is limited to systems using affected AMD 3rd Gen EPYC platforms and applicable AGESA firmware. The source bundle lists versions only as various, so teams must map exposure against AMD-SB-1032 and OEM firmware information.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. Exploitation requires local low-privileged access, which makes multi-user, hosted, or weakly controlled server environments more relevant than isolated systems.
Researcher notes
The public description is sparse. It identifies SMU message-port register validation weakness and potential denial of service, but does not provide affected version granularity, proof-of-concept status, or detailed remediation steps in the supplied bundle.
Mitigation direction
- Review AMD-SB-1032 for affected platform and AGESA guidance.
- Check OEM server firmware advisories for applicable AMD updates.
- Prioritize systems with untrusted local users or shared access.
- Restrict unnecessary local shell access where practical.
- Monitor vendor guidance because fixes are not detailed in the source bundle.
Validation and detection
- Inventory AMD 3rd Gen EPYC systems and firmware levels.
- Compare AGESA or BIOS versions against AMD-SB-1032.
- Confirm whether local low-privileged users can access affected systems.
- Review availability incidents on potentially exposed servers.
- Track remediation status through OEM firmware management tools.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-693: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-26355 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H1.83.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.5MediumVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.amd.com/en/corporate/product-security/bulletin/AMD-SB-1032CVE reference · vendor-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Protection Mechanism Failure
Protection Mechanism Failure represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.