CVE-2021-42143: tinydtls (CVSS 9.1)

Description

An issue was discovered in Contiki-NG tinyDTLS through master branch 53a0d97. An infinite loop bug exists during the handling of a ClientHello handshake message. This bug allows remote attackers to cause a denial of service by sending a malformed ClientHello handshake message with an odd length of cipher suites, which triggers an infinite loop (consuming all resources) and a buffer over-read that can disclose sensitive information.

Is your site exposed to CVE-2021-42143?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

9.1

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Weakness Type (CWE)

CWE-835 CWE-835

Affected Products

Vendor	Product	Versions
contiki-ng	tinydtls	< 2018-08-30

References

Other References

https://seclists.org/fulldisclosure/2024/Jan/16 http://seclists.org/fulldisclosure/2024/Jan/16 https://seclists.org/fulldisclosure/2024/Jan/16

Frequently Asked Questions

What is CVE-2021-42143? +

An issue was discovered in Contiki-NG tinyDTLS through master branch 53a0d97. An infinite loop bug exists during the handling of a ClientHello handshake message. This bug allows remote attackers to cause a denial of service by sending a malformed ClientHello handshake message with an odd length of cipher suites, which triggers an infinite loop (consuming all resources) and a buffer over-read that can disclose sensitive information. It has a CVSS v3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2021-42143? +

CVE-2021-42143 has a CVSS v3.1 score of 9.1 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately.

What products are affected by CVE-2021-42143? +

CVE-2021-42143 affects products from contiki-ng, specifically: tinydtls. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2021-42143? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2025-27497

OpenDJ is an LDAPv3 compliant directory service. OpenDJ prior to 4.9.3 contains a denial-of-service (DoS) vulnerability that causes the server …

CVE-2025-29776

Azle is a WebAssembly runtime for TypeScript and JavaScript on ICP. Calling `setTimer` in Azle versions `0.27.0`, `0.28.0`, and `0.29.0` …

CVE-2025-32029

ts-asn1-der is a collection of utility classes to encode ASN.1 data following DER rule. Incorrect number DER encoding can lead …

CVE-2024-8088

There is a HIGH severity vulnerability affecting the CPython "zipfile" module affecting "zipfile.Path". Note that the more common API "zipfile.ZipFile" …

CVE-2026-41146

facil.io is a C micro-framework for web applications. Prior to commit 5128747363055201d3ecf0e29bf0a961703c9fa0, `fio_json_parse` can enter an infinite loop when it …

CVE-2026-39806

Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in mtrudel bandit allows unauthenticated remote denial of service via worker process …

CVE-2021-42143