CVE-2021-42144Network attack vector

Remote memory disclosure via oversized fragment length

Published Jan 24, 2024 · Updated Jun 20, 2025

Buffer over-read in Contiki-NG tinyDTLS through 2018-08-30 allows remote attackers to disclose sensitive memory via crafted DTLS packets. The server passes an attacker-controlled DTLS fragment length into dtls_ccm_decrypt_message() even when that value exceeds the received packet, causing the decrypt loop to read past the packet buffer. A reachable DTLS server with an existing non-null peer is exposed; the bounded result is disclosure of adjacent process memory.

CVSS severity9.8
Critical
EPSS probability0.66%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer over-read in Contiki-NG tinyDTLS through 2018-08-30 allows remote attackers to disclose sensitive memory via crafted DTLS packets. The server passes an attacker-controlled DTLS fragment length into dtls_ccm_decrypt_message() even when that value exceeds the received packet, causing the decrypt loop to read past the packet buffer. A reachable DTLS server with an existing non-null peer is exposed; the bounded result is disclosure of adjacent process memory.

The record

CVE
CVE-2021-42144
Published
Jan 24, 2024
Updated
Jun 20, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-125, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 24, 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

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

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-125Out-of-bounds Read
T1190Exploit Public-Facing Application

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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