Security readout for executives and security teams
Plain-English summary
This is an AMD firmware validation flaw. Certain malformed size values in firmware binary headers may cause out-of-bounds reads, which can crash affected systems or expose limited memory contents. The cited impact is denial of service and limited confidentiality loss, not code execution or data modification.
Executive priority
Handle this as a high-priority firmware exposure review, especially for critical endpoints or systems where outage has operational impact. There is no cited active exploitation in the provided sources, but the high availability impact supports timely inventory and vendor-guided updates.
Technical view
CVE-2021-26365 is a CWE-125 out-of-bounds read in AMD AGESA firmware signature validation. The CVSS 3.1 vector is 8.2 high, network-accessible, low-complexity, no privileges or user interaction, with low confidentiality and high availability impact. Integrity impact is not reported.
Likely exposure
Exposure is tied to systems using the AMD processor families listed in the CVE source bundle and AGESA firmware. Exact vulnerable AGESA or OEM BIOS versions are not provided here, so organizations must map AMD guidance to their hardware inventory and OEM firmware levels.
Exploitation context
The source bundle does not report active exploitation, and KEV status is false. Treat exploitation status as unconfirmed. The described attack surface involves crafted firmware binary header size values reaching signature validation, with disruption and limited memory disclosure as the cited outcomes.
Researcher notes
Evidence is limited to the CVE record, CVE List entry, and AMD advisory reference. The bundle does not provide precise affected AGESA builds, exploit telemetry, or detailed patch identifiers. Validation should focus on product and firmware mapping rather than reproducing malformed-header behavior.
Mitigation direction
- Review AMD-SB-4001 and applicable OEM BIOS advisories.
- Inventory systems with the listed AMD Ryzen and Athlon platforms.
- Map installed BIOS or firmware versions to AMD and OEM guidance.
- Apply vendor-supported firmware updates where identified as applicable.
- Prioritize business-critical systems where denial of service is high impact.
Validation and detection
- Confirm whether assets use the listed AMD processor families.
- Record motherboard or device OEM, BIOS version, and AGESA version where available.
- Compare firmware levels against AMD-SB-4001 and OEM update notes.
- Check vulnerability management data for CVE-2021-26365 coverage.
- Avoid disruptive malformed-firmware testing on production systems.
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-125: 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-2021-26365 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
- High
- CVSS
- 8.2 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H3.94.2Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.2HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.amd.com/en/corporate/product-security/bulletin/AMD-SB-4001CVE 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.
Out-of-bounds Read
Out-of-bounds Read represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.