CVE-2021-43666
HIGHEPSS 81th pctlDescription
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.
How to fix
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
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Exploit Intelligence
Elevated risk: more likely to be exploited than 81% of all known CVEs.
References
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 |
Common questions
How do I fix CVE-2021-43666?
Upgrade mbedtls on debian 12 to 2.28.0-1 or later.
Is CVE-2021-43666 being actively exploited?
Not that we know of. CVE-2021-43666 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 2.1% is the estimated probability that it will be exploited in the next 30 days. That is higher than 81% of all scored CVEs.
How severe is CVE-2021-43666?
CVE-2021-43666 has a CVSS v3 base score of 7.5, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2021-43666 affect?
Published advisories record a fix for mbedtls (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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Markdown
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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 2026-06-17.