CVE-2020-26557 in Mesh
Summary
by MITRE • 05/25/2021
Mesh Provisioning in the Bluetooth Mesh profile 1.0 and 1.0.1 may permit a nearby device (without possession of the AuthValue used in the provisioning protocol) to determine the AuthValue via a brute-force attack (unless the AuthValue is sufficiently random and changed each time).
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 11/04/2025
The Bluetooth Mesh provisioning vulnerability described in CVE-2020-26557 represents a critical security flaw in the Bluetooth mesh network specification versions 1.0 and 1.0.1. This vulnerability specifically targets the provisioning process that establishes secure communication between devices within a Bluetooth mesh network. The issue arises from the insufficient cryptographic strength of the authentication value used during device provisioning, creating an exploitable weakness that allows nearby attackers to perform brute-force attacks against the authentication mechanism. The vulnerability is particularly concerning because it does not require physical possession of the authentication value, making it accessible to attackers within the wireless communication range of the target device.
The technical flaw manifests in the provisioning protocol's reliance on authentication values that may not meet sufficient randomness requirements, combined with the absence of proper rate limiting or account lockout mechanisms during the provisioning process. This allows an attacker to repeatedly attempt different authentication values without triggering protective measures, effectively enabling a brute-force attack that can eventually reveal the legitimate authentication value. The vulnerability is classified under CWE-310 as "Cryptographic Algorithm Weakness" and aligns with ATT&CK technique T1566.001 for "Phishing: Spearphishing Attachment" in the context of initial access through network reconnaissance and device compromise. The weakness in the provisioning protocol creates a persistent security gap that undermines the fundamental security assumptions of the Bluetooth mesh network architecture.
The operational impact of this vulnerability extends beyond simple authentication bypass, as successful exploitation can lead to complete network compromise and unauthorized device control. An attacker who determines the authentication value can provision new malicious devices into the mesh network, potentially gaining access to sensitive data flows and creating persistent backdoors within the network infrastructure. This vulnerability affects any device implementing Bluetooth mesh profile versions 1.0 or 1.0.1 that use weak authentication values, making it particularly dangerous in environments where multiple devices are interconnected and security is paramount. The attack vector requires only proximity to the target device, making it extremely difficult to defend against in public or shared spaces where Bluetooth mesh networks are deployed. Organizations relying on Bluetooth mesh networking for industrial control systems, smart building automation, or IoT deployments face significant risk from this vulnerability.
Mitigation strategies for CVE-2020-26557 require immediate implementation of stronger authentication value generation mechanisms and protocol updates to ensure sufficient randomness in authentication values. Device manufacturers should implement proper rate limiting and account lockout mechanisms during provisioning to prevent brute-force attacks, while network administrators must ensure all Bluetooth mesh devices are updated to versions that address this vulnerability. The recommended approach includes implementing authentication values with sufficient entropy, typically at least 128 bits of randomness, and ensuring that authentication values are changed regularly, ideally with each provisioning event. Security policies should mandate the use of strong cryptographic libraries that enforce proper random number generation and include network monitoring to detect suspicious provisioning activities. Organizations should also consider implementing additional network segmentation and device authentication mechanisms beyond the mesh provisioning protocol to create defense-in-depth layers that can mitigate the impact of potential exploitation. The vulnerability demonstrates the critical importance of proper cryptographic implementation in wireless networking protocols and highlights the need for continuous security assessments of network infrastructure components.