CVE-2021-43666Public exploitNetwork attack vector

Application hang via zero-length PKCS#12 password

Published Mar 24, 2022 · Updated Dec 2, 2025

Denial of service in Arm Mbed TLS 3.0.0 and earlier allows remote attackers to hang applications via a zero-length PKCS#12 password. The mbedtls_pkcs12_derivation routine mishandles a zero-length password and remains in its derivation loop instead of returning a result or error. Reachability depends on a consuming application passing attacker-controlled password data to this library API; the bounded consequence is an application hang.

CVSS severity7.5
High
EPSS probability2.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Arm Mbed TLS 3.0.0 and earlier allows remote attackers to hang applications via a zero-length PKCS#12 password. The mbedtls_pkcs12_derivation routine mishandles a zero-length password and remains in its derivation loop instead of returning a result or error. Reachability depends on a consuming application passing attacker-controlled password data to this library API; the bounded consequence is an application hang.

The record

CVE
CVE-2021-43666
Published
Mar 24, 2022
Updated
Dec 2, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-130, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 24, 2022CVE publishedPublication date reported by the CVE source.
  2. Dec 2, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-130Improper Handling of Length Parameter Inconsistency
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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