How severe is CVE-2021-26356?

CVE-2021-26356 has a CVSS 3.x base score of 7.4, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2021-26356 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (32nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-26356?

CVE-2021-26356 primarily affects Amd Epyc 7001 Firmware. In total, 98 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-26356?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-26356 published?

CVE-2021-26356 was published on 2023-05-09 and last updated on 2026-06-17.

CVE-2021-26356

CVE-2021-26356 is a high-severity vulnerability in Amd Epyc 7001 Firmware with a CVSS 3.x base score of 7.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-367.

Key facts

Severity: High (CVSS 3.x base score 7.4)
EPSS exploit prediction: 0% (32nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-367
Affected product: Amd Epyc 7001 Firmware
Published: 2023-05-09
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2021-26356?: 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.
How severe is CVE-2021-26356?: CVE-2021-26356 has a CVSS 3.x base score of 7.4, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2021-26356 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (32nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-26356?: CVE-2021-26356 primarily affects Amd Epyc 7001 Firmware. In total, 98 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-26356?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-26356 published?: CVE-2021-26356 was published on 2023-05-09 and last updated on 2026-06-17.

References

Affected products (98)

cpe:2.3:o:amd:epyc_7001_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7251_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7261_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7281_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7301_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7351_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7351p_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7371_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7401_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7401p_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7451_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7501_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7551_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7551p_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7601_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7002_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7232p_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7252_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7262_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7272_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7282_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7302_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7302p_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7352_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7402_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7402p_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7452_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7502_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7532_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7542_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7552_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7642_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7662_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7702_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7702p_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7f32_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7f52_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7f72_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7h12_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:amd:epyc_7742_firmware:*:*:*:*:*:*:*:*

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