CVE-2020-36421

MEDIUMNVD 5.35.3—

5.3

An issue was discovered in Arm Mbed TLS before 2.23.0. Because of a side channel in modular exponentiation, an RSA private key used in a secure enclave could be disclosed.

CVSS v3: 5.3
EG Score: 5.3(medium)
EPSS: 67.0%
KEV: Not listed

Published

July 19, 2021

Last Modified

December 3, 2025

References (10)

cve@mitrehttps://bugs.gentoo.org/730752
cve@mitrehttps://github.com/ARMmbed/mbedtls/issues/3394
cve@mitrehttps://github.com/ARMmbed/mbedtls/releases/tag/v2.16.7
cve@mitrehttps://github.com/ARMmbed/mbedtls/releases/tag/v2.23.0
cve@mitrehttps://lists.debian.org/debian-lts-announce/2022/12/msg00036.html
af854a3a-2127-422b-91ae-364da2661108https://bugs.gentoo.org/730752
af854a3a-2127-422b-91ae-364da2661108https://github.com/ARMmbed/mbedtls/issues/3394
af854a3a-2127-422b-91ae-364da2661108https://github.com/ARMmbed/mbedtls/releases/tag/v2.16.7
af854a3a-2127-422b-91ae-364da2661108https://github.com/ARMmbed/mbedtls/releases/tag/v2.23.0
af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2022/12/msg00036.html

Weakness Classification(1)

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

CWE-203Observable Discrepancy (Information Exposure via Side Channel)

Data Freshness Timeline

(refreshed 10× in last 7d / 18× 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 20:11 UTCepss_batch
2026-06-02 20:11 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
2026-05-31 22:29 UTCepss_batch
2026-05-31 22:29 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-29 13:42 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 13:23 UTCEG score recompute
2026-05-26 13:23 UTCGHSA enrichment
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch

Frequently asked(5)

What is CVE-2020-36421?

CVE-2020-36421 is a medium vulnerability published on July 19, 2021. An issue was discovered in Arm Mbed TLS before 2.23.0. Because of a side channel in modular exponentiation, an RSA private key used in a secure enclave could be disclosed.

When was CVE-2020-36421 disclosed?

CVE-2020-36421 was first published in the National Vulnerability Database on July 19, 2021, with the most recent update on December 3, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2020-36421 actively exploited?

CVE-2020-36421 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 67.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2020-36421?

CVE-2020-36421 has a CVSS v3 base score of 5.3 (NVD).

How do I remediate CVE-2020-36421?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2020-36421, 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.

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CVE-2020-36421

📅 Published

🔄 Last Modified

🔗 References (10)

Weakness Classification(1)

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2020-36421?

🔗 Related CVEs(same CWE)

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Published

Last Modified

References (10)

Frequently asked(5)

Related CVEs(same CWE)