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% (80th 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 80th 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

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

80thpercentile

Elevated risk: more likely to be exploited than 80% of all known CVEs.

References

Exploit1

github.com

Third-Party Advisory1

lists.debian.org

Other references1

lists.debian.org

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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.