Cyber Resilience

CVE-2021-26356

High

Published: 09 May 2023

Published
09 May 2023
Modified
28 January 2025
KEV Added
—
Patch
—
CVSS Score v3.1 7.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS Score 0.0027 50.8th percentile
Risk Priority 15 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2021-26356 is a high-severity Time-of-check Time-of-use (TOCTOU) Race Condition (CWE-367) vulnerability in Amd Epyc 7001 Firmware. Its CVSS base score is 7.4 (High).

Operationally, ranked in the top 49.2% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability details

A TOCTOU in ASP bootloader may allow an attacker to tamper with the SPI ROM following data read to memory potentially resulting in S3 data corruption and information disclosure.

CWE(s)
CWE-367

Related Threats

No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.

Affected Assets

amd
epyc 7001 firmware
≤ naplespi_1.0.0.h
amd
epyc 7251 firmware
≤ naplespi_1.0.0.h
amd
epyc 7261 firmware
≤ naplespi_1.0.0.h
amd
epyc 7281 firmware
≤ naplespi_1.0.0.h
amd
epyc 7301 firmware
≤ naplespi_1.0.0.h
amd
epyc 7351 firmware
≤ naplespi_1.0.0.h
amd
epyc 7351p firmware
≤ naplespi_1.0.0.h
amd
epyc 7371 firmware
≤ naplespi_1.0.0.h
amd
epyc 7401 firmware
≤ naplespi_1.0.0.h
amd
epyc 7401p firmware
≤ naplespi_1.0.0.h
+88 more product configuration(s) — see NVD for full list

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

AU-8 Time Stamps
addresses: CWE-367

Timestamps meeting UTC or offset standards help identify TOCTOU issues through precise chronological reconstruction of check/use operations.

References