CVE-2021-40830

MQTT broker spoofing via appended system trust roots

Published Nov 22, 2021 · Updated Aug 4, 2024

Improper certificate validation in AWS IoT Device SDK v2 and AWS-C-IO on Unix systems allows attackers to spoof MQTT brokers. The aws_tls_ctx_options_override_default_trust_store functions append a supplied CA to system roots, so TLS also accepts peers trusted only by the host store. Affected releases are Java before 1.5.0, Python before 1.6.1, C++ before 1.12.7, Node.js before 1.5.3, and AWS-C-IO 0.10.4; exploitation requires trust-store access or a compromised trusted CA plus DNS spoofing and permits forged replies or dropped traffic.

CVSS severity6.3
Medium
EPSS probability0.39%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in AWS IoT Device SDK v2 and AWS-C-IO on Unix systems allows attackers to spoof MQTT brokers. The aws_tls_ctx_options_override_default_trust_store functions append a supplied CA to system roots, so TLS also accepts peers trusted only by the host store. Affected releases are Java before 1.5.0, Python before 1.6.1, C++ before 1.12.7, Node.js before 1.5.3, and AWS-C-IO 0.10.4; exploitation requires trust-store access or a compromised trusted CA plus DNS spoofing and permits forged replies or dropped traffic.

The record

CVE
CVE-2021-40830
Published
Nov 22, 2021
Updated
Aug 4, 2024
Vendor
Amazon Web Services
Product
AWS IoT Device SDK v2 for Python
Classifications
CWE-295, T1557
Attack vector
adjacent
Privileges
admin

Timeline

How it unfolded

  1. Nov 22, 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 <1.6.1

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesadmin

What is affected?

Amazon Web Services · AWS IoT Device SDK v2 for Pythonversion=unspecified <1.6.1
Amazon Web Services · AWS IoT Device SDK v2 for C++version=unspecified <1.12.7
Amazon Web Services · AWS-C-IOversion=0.10.4
Amazon Web Services · AWS IoT Device SDK v2 for Javaversion=unspecified <1.5.0
Amazon Web Services · AWS IoT Device SDK v2 for Node.jsversion=unspecified <1.5.3

Published CVSS scores

7.3GitHubCVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
6.3F-SecureCVSS:3.1/AV:A/AC:H/PR:H/UI:R/S:U/C:H/I:H/A:H
8.8NIST NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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)
Vectoradjacent
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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