CVE-2023-20521

LOWNVD 3.35.7▲

3.3

TOCTOU in the ASP Bootloader may allow an attacker with physical access to tamper with SPI ROM records after memory content verification, potentially leading to loss of confidentiality or a denial of service.

CVSS v3: 3.3
EG Score: 5.7(medium)
EPSS: 17.6%
KEV: Not listed

Published

November 14, 2023

Last Modified

November 21, 2024

References (6)

psirt@amdhttps://www.amd.com/en/corporate/product-security/bulletin/AMD-SB-3002
psirt@amdhttps://www.amd.com/en/corporate/product-security/bulletin/AMD-SB-4002
psirt@amdhttps://www.amd.com/en/corporate/product-security/bulletin/AMD-SB-5001
af854a3a-2127-422b-91ae-364da2661108https://www.amd.com/en/corporate/product-security/bulletin/AMD-SB-3002
af854a3a-2127-422b-91ae-364da2661108https://www.amd.com/en/corporate/product-security/bulletin/AMD-SB-4002
af854a3a-2127-422b-91ae-364da2661108https://www.amd.com/en/corporate/product-security/bulletin/AMD-SB-5001

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition

Data Freshness Timeline

(refreshed 14× in last 7d / 20× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-06-02 20:12 UTCepss_batch
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2026-06-01 13:51 UTCepss_batch
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2026-05-29 13:43 UTCepss_batch
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2026-05-28 13:43 UTCepss_batch
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2026-05-27 13:39 UTCepss_batch
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2026-05-26 07:18 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch

Frequently asked(5)

What is CVE-2023-20521?

CVE-2023-20521 is a low vulnerability published on November 14, 2023. TOCTOU in the ASP Bootloader may allow an attacker with physical access to tamper with SPI ROM records after memory content verification, potentially leading to loss of confidentiality or a denial of service.

When was CVE-2023-20521 disclosed?

CVE-2023-20521 was first published in the National Vulnerability Database on November 14, 2023, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2023-20521 actively exploited?

CVE-2023-20521 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 17.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2023-20521?

CVE-2023-20521 has a CVSS v3 base score of 3.3 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 5.7.

How do I remediate CVE-2023-20521?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2023-20521, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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CVE-2023-20521

📅 Published

🔄 Last Modified

🔗 References (6)

Weakness Classification(1)

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2023-20521?

🔗 Related CVEs(same CWE)

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Published

Last Modified

References (6)

Frequently asked(5)

Related CVEs(same CWE)