WhatsApp Multi-Device Mode Exposed Critical Device Fingerprinting Vulnerability for Years

15.01.2026

WhatsApp, owned by Meta, has long been identified as a convenient entry point for sophisticated cyberattacks, according to security researchers.

A critical vulnerability in the service's multi-device mode has been exposing technical information about users' devices for several years, enabling threat actors to perform device fingerprinting during the reconnaissance phase of targeted attacks.

Security experts have demonstrated that WhatsApp's implementation allowed attackers to extract sufficiently detailed technical specifications to identify specific devices and their operating systems before launching exploits.

The attack vector leveraged cryptographic key parameters to perform accurate device fingerprinting. By analyzing specific characteristics of cryptographic keys exchanged during multi-device synchronization, adversaries could determine:

• The specific device model being used
• The operating system running on the target device
• Platform-specific information useful for tailoring exploits

Every sophisticated cyberattack begins with reconnaissance — before deploying an exploit, threat actors need to understand what device is on the other end of the communication channel. This vulnerability essentially provided that critical intelligence without requiring any sophisticated exploitation techniques.

The fingerprinting capability exposed by WhatsApp's multi-device architecture represents a significant operational security risk, as it enables attackers to profile targets and select appropriate attack vectors with high precision.

Sources:
https://www.usenix.org/conference/woot24/presentation/beery
https://www.securitylab.ru/news/567859.php

Tags: Meta WhatsApp Cryptography vulnerability device fingerprinting

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