CVE-2021-40831

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

Severity Score

7.2

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

*SSVC

Descriptions

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.

El SDK de dispositivos de AWS IoT v2 para Java, Python, C++ y Node.js añade una autoridad de certificación (CA) suministrada por el usuario a las CA root en lugar de anularla en los sistemas macOS. Además, la comprobación SNI tampoco está habilitada cuando la CA ha sido "overridden". Por lo tanto, los handshakes TLS tendrán éxito si el peer puede ser verificado desde la CA suministrada por el usuario o desde el trust-store por defecto del sistema. Los atacantes con acceso a los almacenes confiables de un host o que puedan comprometer una autoridad de certificación que ya esté en el almacén confiable del host (nota: el atacante también debe ser capaz de falsificar el DNS en este caso) pueden ser capaces de usar este problema para omitir el pinning de la CA. Un atacante podría entonces falsificar el broker MQTT, y dejar caer el tráfico y/o responder con los datos del atacante, pero no sería capaz de reenviar estos datos al broker MQTT porque el atacante todavía necesitaría las claves privadas del usuario para autenticarse contra el broker MQTT. La función "aws_tls_ctx_options_override_default_trust_store_*" dentro del submódulo aws-c-io ha sido actualizada para abordar este comportamiento. Este problema afecta a: Amazon Web Services AWS IoT Device SDK v2 para versiones de Java anteriores a 1.5.0 en macOS. Amazon Web Services AWS IoT Device SDK v2 para versiones de Python anteriores a 1.7.0 en macOS. Amazon Web Services AWS IoT Device SDK v2 para versiones de C++ anteriores a 1.14.0 en macOS. Amazon Web Services AWS IoT Device SDK v2 para versiones de Node.js anteriores a 1.6.0 en macOS. Amazon Web Services AWS-C-IO 0.10.7 en macOS

*Credits: F-Secure

CVSS Scores

Attack Vector

Network

Attack Complexity

Low

Privileges Required

High

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Attack Vector

Adjacent

Attack Complexity

High

Privileges Required

High

User Interaction

Required

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Attack Vector

Network

Attack Complexity

Medium

Authentication

Single

Confidentiality

Partial

Integrity

Partial

Availability

Partial

* Common Vulnerability Scoring System

SSVC

Decision:-

Exploitation

Automatable

Tech. Impact

* Organization's Worst-case Scenario

Timeline

2021-09-09 CVE Reserved
2021-11-22 CVE Published
2023-10-09 EPSS Updated
2024-08-04 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-295: Improper Certificate Validation

CAPEC

References (5)

URL	Tag	Source
https://github.com/aws/aws-iot-device-sdk-cpp-v2	Product
https://github.com/aws/aws-iot-device-sdk-java-v2	Product
https://github.com/aws/aws-iot-device-sdk-js-v2	Product
https://github.com/aws/aws-iot-device-sdk-python-v2	Product
https://github.com/awslabs/aws-c-io	Product

URL	Date	SRC

URL	Date	SRC

URL	Date	SRC

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Amazon Search vendor "Amazon"	Amazon Web Services Aws-c-io Search vendor "Amazon" for product "Amazon Web Services Aws-c-io"	0.10.7 Search vendor "Amazon" for product "Amazon Web Services Aws-c-io" and version "0.10.7"	-	Affected	in	Apple Search vendor "Apple"	Macos Search vendor "Apple" for product "Macos"	-	-	Safe
Amazon Search vendor "Amazon"	Amazon Web Services Internet Of Things Device Software Development Kit V2 Search vendor "Amazon" for product "Amazon Web Services Internet Of Things Device Software Development Kit V2"	< 1.5.0 Search vendor "Amazon" for product "Amazon Web Services Internet Of Things Device Software Development Kit V2" and version " < 1.5.0"	java	Affected	in	Apple Search vendor "Apple"	Macos Search vendor "Apple" for product "Macos"	-	-	Safe
Amazon Search vendor "Amazon"	Amazon Web Services Internet Of Things Device Software Development Kit V2 Search vendor "Amazon" for product "Amazon Web Services Internet Of Things Device Software Development Kit V2"	< 1.6.0 Search vendor "Amazon" for product "Amazon Web Services Internet Of Things Device Software Development Kit V2" and version " < 1.6.0"	node.js	Affected	in	Apple Search vendor "Apple"	Macos Search vendor "Apple" for product "Macos"	-	-	Safe
Amazon Search vendor "Amazon"	Amazon Web Services Internet Of Things Device Software Development Kit V2 Search vendor "Amazon" for product "Amazon Web Services Internet Of Things Device Software Development Kit V2"	< 1.7.0 Search vendor "Amazon" for product "Amazon Web Services Internet Of Things Device Software Development Kit V2" and version " < 1.7.0"	python	Affected	in	Apple Search vendor "Apple"	Macos Search vendor "Apple" for product "Macos"	-	-	Safe
Amazon Search vendor "Amazon"	Amazon Web Services Internet Of Things Device Software Development Kit V2 Search vendor "Amazon" for product "Amazon Web Services Internet Of Things Device Software Development Kit V2"	< 1.14.0 Search vendor "Amazon" for product "Amazon Web Services Internet Of Things Device Software Development Kit V2" and version " < 1.14.0"	c\+\+	Affected	in	Apple Search vendor "Apple"	Macos Search vendor "Apple" for product "Macos"	-	-	Safe