Pierluigi Paganini August 08, 2019

Security experts at CheckPoint discovered a series of vulnerabilities in WhatsApp that could be exploited by attackers to tamper with conversations.

A team of Check Point security researchers composed of Dikla Barda, Roman Zaikin, and Oded Vanunu devised three attacks that leverage the vulnerabilities in WhatsApp to tamper with conversations.

The flaws could allow attackers to intercept and manipulate messages by WhatApp users sent in both private and group conversations. Experts warn of possible abuse of the attack techniques to spread misinformation targeting trusted sources.

Vanunu explained at the Black Hat conference in Las Vegas, Nevada, that the vulnerabilities were responsibly disclosed in 2018, but remained exploitable for a long time.

“Check Point Research, however, recently unveiled new vulnerabilities in the popular messaging application that could allow threat actors to intercept and manipulate messages sent in both private and group conversations, giving attackers immense power to create and spread misinformation from what appear to be trusted sources.” reads the post published by CheckPoint.

The Financial Times reported that according to Facebook, which owns WhatsApp, the vulnerabilities were due to “limitations that can’t be solved due to their structure and architecture.”

WhatsApp encrypts every message, picture, call, video or any other type of content that could be sent in a conversation and allows only the recipient to decrypt it.

The experts made a reverse engineering of the algorithm used by the popular application to decrypt the data and discovered that WhatsApp is using the “protobuf2 protocol” to do so. Then they were able to convert the protobuf2 data to JSON to see the actual parameters that are sent and attempt to manipulate them for testing purposes.

The experts created a Burp Suit Extension that presented at the Black Hat conference and devised 3 manipulation methods to carry out the attack.

“Our team observed three possible methods of attack exploiting this vulnerability – all of which involve social engineering tactics to fool end-users.” continues the post. “A threat actor can:

1. Use the ‘quote’ feature in a group conversation to change the identity of the sender, even if that person is not a member of the group.
2. Alter the text of someone else’s reply, essentially putting words in their mouth.
3. Send a private message to another group participant that is disguised as a public message for all, so when the targeted individual responds, it’s visible to everyone in the conversation.“

Currently, only the issue associated with the transmission of the private message to public message seems to have been resolved by Facebook, the remaining two problems are still effective. 

“It’s a vulnerability that allows a malicious user to create fake news and create fraud,” Mr Vanunu told BBC.

“You can completely change what someone says,” Mr Vanunu added. “You can completely manipulate every character in the quote.”

Check Point decided to disclose the flaws due to the extent of the vulnerabilities.

“[WhatsApp] serves 30 percent of the global population. It’s our responsibility. There is a big problem with fake news and manipulation. It’s infrastructure that serves more than 1.5 billion users. We cannot like put it aside and say: ‘Okay, this is not happening.'” Vanunu told the BBC

Check Point published technical details of the flaws and detailed their exploitation here.

Pierluigi Paganini

(SecurityAffairs – WhatsApp, hacking)

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