CVE-2020-26559 in Mesh
Summary
by MITRE • 05/25/2021
Bluetooth Mesh Provisioning in the Bluetooth Mesh profile 1.0 and 1.0.1 may permit a nearby device (participating in the provisioning protocol) to identify the AuthValue used given the Provisioner’s public key, and the confirmation number and nonce provided by the provisioning device. This could permit a device without the AuthValue to complete provisioning without brute-forcing the AuthValue.
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Analysis
by VulDB Data Team • 11/04/2025
The vulnerability CVE-2020-26559 affects the Bluetooth Mesh provisioning protocol version 1.0 and 1.0.1, specifically targeting the security mechanisms that protect the authentication value during device provisioning. This weakness resides in the cryptographic implementation of the Bluetooth Mesh profile, which is designed to establish secure communication networks between IoT devices through a mesh topology. The provisioning process involves a complex cryptographic handshake where devices exchange public keys, confirmation numbers, and nonces to authenticate and establish secure connections. When a malicious device comes within proximity of a legitimate provisioning process, it can exploit the mathematical relationships between the exchanged cryptographic parameters to deduce the authentication value without resorting to brute force attacks.
The technical flaw stems from insufficient cryptographic security in the Bluetooth Mesh provisioning algorithm, where the confirmation procedure does not adequately protect the AuthValue from passive observation and analysis. The vulnerability occurs because the protocol's design allows an attacker to perform a mathematical analysis of the public key, confirmation value, and nonce that are exchanged during the provisioning process. This cryptographic weakness creates a scenario where an attacker with knowledge of the public key and the two cryptographic values can compute the AuthValue through mathematical inversion, effectively bypassing the intended authentication mechanism. The issue is particularly concerning because it operates at the protocol level rather than requiring active exploitation or complex attack vectors.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it fundamentally undermines the security model of Bluetooth Mesh networks. An attacker positioned near a provisioning device can complete the provisioning process without knowing the actual authentication value, potentially gaining unauthorized access to the entire mesh network. This capability allows for the insertion of malicious devices into secure networks, enabling potential man-in-the-middle attacks, data interception, or complete network compromise. The vulnerability affects all devices implementing Bluetooth Mesh profile versions 1.0 and 1.0.1, creating widespread exposure across various IoT deployments including smart buildings, industrial automation systems, and wireless sensor networks. Organizations relying on Bluetooth Mesh for security-critical applications face significant risk of unauthorized network access and data breaches.
Mitigation strategies for this vulnerability require immediate implementation of firmware updates from device manufacturers, as the issue lies within the core Bluetooth Mesh protocol implementation. Organizations should also consider deploying additional network monitoring solutions to detect anomalous provisioning activities and establish strict physical security controls around provisioning processes. The remediation approach must include upgrading to Bluetooth Mesh profile version 1.1 or later, which addresses this cryptographic weakness through improved confirmation procedures. Security teams should implement network segmentation and access controls to limit the impact if an attacker successfully provisions a malicious device. This vulnerability aligns with CWE-310 and CWE-326 categories related to cryptographic weaknesses and insufficient encryption strength, while also mapping to ATT&CK techniques involving initial access through network service exploitation and privilege escalation through authentication bypass methods.