Is CVE-2021-43666 in the CISA KEV catalog?

No. CVE-2021-43666 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-43666?

CVE-2021-43666 has a CVSS v3 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2021-43666?

CVE-2021-43666 has an EPSS score of 2.21% (81th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-43666?

Upgrade mbedtls on debian 11 to 2.16.9-0.1+deb11u1 or later.

CVE & CISA-KEV Catalog

CVE-2021-43666

HIGHEPSS 81th pctl

7.5

CVSS v3

NVD

Description

A Denial of Service vulnerability exists in mbed TLS 3.0.0 and earlier in the mbedtls_pkcs12_derivation function when an input password's length is 0.

CWE-130

How to fix

Remediation Available

mbedtlsDebian

Fixed in:2.16.9-0.1+deb11u1CVE-2021-43666

Fixed in:2.28.0-1CVE-2021-43666

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploit Intelligence

2.21%probability of exploitation in 30 days

81stpercentile

Elevated risk: more likely to be exploited than 81% of all known CVEs.

References

Exploit1

github.com

Third-Party Advisory1

lists.debian.org

Other references1

lists.debian.org

Related Vulnerabilities

Other CWE-130 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-14847	High	7.5	83%	KEV	Fix
CVE-2024-39614	High	7.5	29%	-	Fix
CVE-2021-36090	High	7.5	13%	-	Fix
CVE-2021-35516	High	7.5	12%	-	Fix
CVE-2021-35517	High	7.5	11%	-	Fix
CVE-2019-3862	High	7.3	8.1%	-	Fix

Embed a live status badge for CVE-2021-43666

Markdown

[![CVE-2021-43666](https://tridentstack.com/cve/badge/CVE-2021-43666.svg)](https://tridentstack.com/cve/CVE-2021-43666)

HTML

<a href="https://tridentstack.com/cve/CVE-2021-43666"><img src="https://tridentstack.com/cve/badge/CVE-2021-43666.svg" alt="CVE-2021-43666"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

See how it works Start freeThis CVE lookup is free and always will be.

This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-12-02.