CVE-2021-42141Network attack vector

Unauthenticated service interruption via mismatched handshake epochs

Published Jan 22, 2024 · Updated Jun 20, 2025

Improper exceptional-condition handling in Contiki-NG tinyDTLS through 2018-08-30 allows remote attackers to interrupt DTLS service. The DTLS server accepts a ClientKeyExchange epoch that differs from the preceding ClientHello epoch and incorrectly emits ChangeCipherSpec, completing an inconsistent handshake. No authentication or user interaction is required; the documented consequence is denial of service, while public sources do not identify the interruption as a hang or crash.

CVSS severity7.5
High
EPSS probability1.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper exceptional-condition handling in Contiki-NG tinyDTLS through 2018-08-30 allows remote attackers to interrupt DTLS service. The DTLS server accepts a ClientKeyExchange epoch that differs from the preceding ClientHello epoch and incorrectly emits ChangeCipherSpec, completing an inconsistent handshake. No authentication or user interaction is required; the documented consequence is denial of service, while public sources do not identify the interruption as a hang or crash.

The record

CVE
CVE-2021-42141
Published
Jan 22, 2024
Updated
Jun 20, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-755, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 22, 2024CVE publishedPublication date reported by the CVE source.
  2. Jun 20, 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

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-755Improper Handling of Exceptional Conditions
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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