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Fencer Intel
medium 6.3

CVE-2021-40831 json

Missing SNI validation and inconsistent CA override function behavior within AWS IoT Device SDKs on Apple devices

published 4y ago modified 4mo ago also GHSA-j3f7-7rmc-6wqj , PYSEC-2021-864 , EUVD-2021-0031

cvss
6.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 50%
public exploits
0
none known

Summary

The AWS IoT Device SDK v2 for Java, Python, C++ and Node.js appends a user supplied Certificate Authority (CA) to the root CAs instead of overriding it on macOS systems. Additionally, SNI validation is also not enabled when the CA has been “overridden”. TLS handshakes will thus succeed if the peer can be verified either from the user-supplied CA or the system’s default trust-store. Attackers with access to a host’s trust stores or are able to compromise a certificate authority already in the host's trust store (note: the attacker must also be able to spoof DNS in this case) may be able to use this issue to bypass CA pinning. An attacker could then spoof the MQTT broker, and either drop traffic and/or respond with the attacker's data, but they would not be able to forward this data on to the MQTT broker because the attacker would still need the user's private keys to authenticate against the MQTT broker. The 'aws_tls_ctx_options_override_default_trust_store_*' function within the aws-c-io submodule has been updated to address this behavior. This issue affects: Amazon Web Services AWS IoT Device SDK v2 for Java versions prior to 1.5.0 on macOS. Amazon Web Services AWS IoT Device SDK v2 for Python versions prior to 1.7.0 on macOS. Amazon Web Services AWS IoT Device SDK v2 for C++ versions prior to 1.14.0 on macOS. Amazon Web Services AWS IoT Device SDK v2 for Node.js versions prior to 1.6.0 on macOS. Amazon Web Services AWS-C-IO 0.10.7 on macOS.

Patch / fix

  • maven software.amazon.awssdk.iotdevicesdk:aws-iot-device-sdk 1.5.0
  • npm aws-iot-device-sdk-v2 1.6.0
  • pypi awsiotsdk 1.7.0
  • Amazon Web Services AWS IoT Device SDK v2 for Java 1.5.0
  • Amazon Web Services AWS IoT Device SDK v2 for Python 1.7.0
  • Amazon Web Services AWS IoT Device SDK v2 for C++ 1.14.0
  • Amazon Web Services AWS IoT Device SDK v2 for Node.js 1.6.0

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Exploit prediction

0.64% chance of exploitation in the next 30 days, higher than 50% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 6.3 CVSS:3.1/AV:A/AC:H/PR:H/UI:R/S:U/C:H/I:H/A:H
NVD 3.1 7.2 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 6.0 AV:N/AC:M/Au:S/C:P/I:P/A:P
GitHub 3.1 6.3 CVSS:3.1/AV:A/AC:H/PR:H/UI:R/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
maven software.amazon.awssdk.iotdevicesdk:aws-iot-device-sdk
<1.5.0
1.5.0
npm aws-iot-device-sdk-v2
<1.6.0
1.6.0
pypi awsiotsdk
<1.7.0
1.7.0

Affected products

  • Amazon Web Services AWS IoT Device SDK v2 for Java
  • Amazon Web Services AWS IoT Device SDK v2 for Python
  • Amazon Web Services AWS IoT Device SDK v2 for C++
  • Amazon Web Services AWS IoT Device SDK v2 for Node.js
  • Amazon Web Services AWS-C-IO

Classification

Weakness
  • CWE-295 Improper Certificate Validation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.