CVE-2021-40828: TLS hostname validation issues within AWS IoT Device SDKs on Windows

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-11-23 · updated 2026-06-17
Weakness: CWE-295

Description

Connections initialized by the AWS IoT Device SDK v2 for Java (versions prior to 1.3.3), Python (versions prior to 1.5.18), C++ (versions prior to 1.12.7) and Node.js (versions prior to 1.5.1) did not verify server certificate hostname during TLS handshake when overriding Certificate Authorities (CA) in their trust stores on Windows. This issue has been addressed in aws-c-io submodule versions 0.9.13 onward. This issue affects: Amazon Web Services AWS IoT Device SDK v2 for Java versions prior to 1.3.3 on Microsoft Windows. Amazon Web Services AWS IoT Device SDK v2 for Python versions prior to 1.5.18 on Microsoft Windows. Amazon Web Services AWS IoT Device SDK v2 for C++ versions prior to 1.12.7 on Microsoft Windows. Amazon Web Services AWS IoT Device SDK v2 for Node.js versions prior to 1.5.3 on Microsoft Windows.

Affected products

Amazon Web Services Aws-C-Io: before 0.9.13 — fixed in 0.9.13
Amazon Web Services Internet Of Things Device Software Development Kit V2: before 1.3.3; before 1.5.1; before 1.5.18; before 1.12.7 — fixed in 1.12.7, 1.3.3, 1.5.1, 1.5.18

How to fix

Upgrade to a fixed version: Amazon Web Services Aws-C-Io 0.9.13; Amazon Web Services Internet Of Things Device Software Development Kit V2 1.12.7, 1.3.3, 1.5.1, 1.5.18. Check the vendor advisory for mitigations.

References

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