The vulnerability is a memory heap overflow issue that was discovered by Google Project Zero white hat hacker Natalie Silvanovich in August. A malformed RTP (Real-time Transport Protocol) packet sent to a user, a call request, could have been used to trigger the memory overflow and cause the crash of the application. It affects both the Android and iPhone clients and WhatsApp has fixed the flaw on September 28. The vulnerability was very trivial, exploitation of the flaw was trivial. An attacker could completely hijack a targets WhatsApp account and spy on its conversations.”]
Source: https://securityaffairs.co/wordpress/76997/hacking/whatsapp-hack-video-call.html