NVD / CVE Program· CNA F-SecureUS

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

Noroxi assessment

Priority: Monitor (action score 35/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.41% (FIRST EPSS).
Someone on the same network segment can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
Fixed version: software.amazon.awssdk.iotdevicesdk:aws-iot-device-sdk (Maven) 1.3.3; aws-iot-device-sdk-v2 (npm) 1.5.1; awsiotsdk (PyPI) 1.5.18.
Severity is disputed: the assigning authority (CNA) scores it 6.3, NVD 8.8.

Low priority for now. Upgrade to software.amazon.awssdk.iotdevicesdk:aws-iot-device-sdk (Maven) 1.3.3; aws-iot-device-sdk-v2 (npm) 1.5.1; awsiotsdk (PyPI) 1.5.18 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 8.8 · v3.1—No exploit Fix available

Published: Nov 22, 2021
Updated: Jun 17, 2026
EPSS: 0.4% · 35th percentile
CWE: CWE-295

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 35 / 40 · 8.8 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.4%

CNA vs NVD score

NVD: 8.8
CNA · F-SecureUS: 6.3; 2.5 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
amazon	amazon web services aws-c-io	cpe:2.3:a:amazon:amazon_web_services_aws-c-io
amazon	amazon web services internet of things device software development kit v2	cpe:2.3:a:amazon:amazon_web_services_internet_of_things_device_software_development_kit_v2
microsoft	windows	cpe:2.3:o:microsoft:windows

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Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

amazon amazon web services aws-c-iobefore 0.9.13
amazon amazon web services internet of things device software development kit v2before 1.3.3
amazon amazon web services internet of things device software development kit v2before 1.5.1
amazon amazon web services internet of things device software development kit v2before 1.5.18
amazon amazon web services internet of things device software development kit v2before 1.12.7

Versions reported by the vendor

Affected version ranges reported by the assigning authority (F-SecureUS). Independent of NVD's CPE analysis and usually ahead of it.

Amazon Web Services AWS IoT Device SDK v2 for C++
- unspecified and later · before 1.12.7affected
Amazon Web Services AWS IoT Device SDK v2 for Java
- unspecified and later · before 1.3.3affected
Amazon Web Services AWS IoT Device SDK v2 for Node.js
- unspecified and later · before 1.5.3affected
Amazon Web Services AWS IoT Device SDK v2 for Python
- unspecified and later · before 1.5.18affected
Amazon Web Services AWS-C-IO
- 0.9.12affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Maven	software.amazon.awssdk.iotdevicesdk:aws-iot-device-sdk	before 1.3.3	1.3.3
npm	aws-iot-device-sdk-v2	before 1.5.1	1.5.1
PyPI	awsiotsdk	before 1.5.18	1.5.18

Same product

amazon: all records

Other highest-scoring records for the same primary product.

CVE-2021-40830Inconsistent CA override function behavior within AWS IoT Device SDKs on Unix systems
35Monitor
CVE-2021-40831Missing SNI validation and inconsistent CA override function behavior within AWS IoT Device SDKs on Apple devices
28Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
Maven:software.amazon.awssdk.iotdevicesdk:aws-iot-device-sdk	1.3.3	Package registry (OSV)
npm:aws-iot-device-sdk-v2	1.5.1	Package registry (OSV)
PyPI:awsiotsdk	1.5.18	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

F-Secure

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

Technical details

Attack conditions

Someone on the same network segment can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: high · data can be read
Integrity: high · data or configuration can be modified
Availability: high · the service can be disrupted

Attack vector: Adjacent
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: High

Weakness class (CWE)

CWE-295 · Improper Certificate Validation

CVSS vector

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

nvd-primary

Root cause

A certificate validation error is silently swallowed instead of terminating the connection. Often, code added for a test environment makes its way into production.

The bug in code

The whole CWE-295 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

kotlin

1override fun checkServerTrusted(chain: Array<X509Certificate>, type: String) {
2  // Left empty for the test environment
3}

Fixed

kotlin

1val client = OkHttpClient.Builder()
2  .certificatePinner(
3    CertificatePinner.Builder()
4      .add("api.sirius.example", "sha256/…")
5      .build()
6  ).build()

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

—

Change log

Fix✗ → ✓Sep 28, 2026, 10:45 PM UTC

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References

github.com/aws/aws-iot-device-sdk-cpp-v2

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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