CVE-2021-34430Network attack vector

Remote DTLS traffic decryption via predictable rand

Published Jul 8, 2021 · Updated Aug 4, 2024

Eclipse TinyDTLS through 0.9-rc1 allows remote attackers to decrypt DTLS traffic by computing the master key. Its key-generation path relies on the C library rand function, producing predictable values that reduce DTLS key secrecy. The attack is network-based and unauthenticated, and the demonstrated consequence is confidentiality loss of protected DTLS communications without integrity or availability impact.

CVSS severity7.5
High
EPSS probability1.04%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Eclipse TinyDTLS through 0.9-rc1 allows remote attackers to decrypt DTLS traffic by computing the master key. Its key-generation path relies on the C library rand function, producing predictable values that reduce DTLS key secrecy. The attack is network-based and unauthenticated, and the demonstrated consequence is confidentiality loss of protected DTLS communications without integrity or availability impact.

The record

CVE
CVE-2021-34430
Published
Jul 8, 2021
Updated
Aug 4, 2024
Vendor
The Eclipse Foundation
Product
tinydtls
Classifications
CWE-338, CWE-326, T1040
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 8, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <=0.9-rc1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Eclipse Foundation · tinydtlsversion=unspecified <=0.9-rc1

Published CVSS scores

5.0NVDAV:N/AC:L/Au:N/C:P/I:N/A:N
7.5NVDCVSS: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-338Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)
CWE-326Inadequate Encryption Strength
T1040Network Sniffing

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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