Instant messaging app Telegram, known for its end-to-end encryption features, was found to contain a bug that would leak users' IP addresses. A security researcher discovered that the Telegram desktop app was leaking public and private IP addresses of users during voice calls. Additionally, users did not have an option to turn off the feature that could potentially leave them vulnerable to cyber-attacks. However, Telegram has reportedly fixed the bug in its latest updates. Notably, the company's security team has awarded the researcher EUR 2,000 (roughly Rs. 1,68,900) for reporting the bug in the app.
Security researcher Dhiraj Mishra reported the Telegram bug, which he says was causing the desktop app to be leaking both public and private IP addresses during voice calls to be made over a P2P (peer-to-peer) framework. While smartphone users have the option of turning off P2P calls by changing the settings to other options by going to Settings > Privacy and security > Calls > Peer-To-Peer, there was no such option available for Telegram users on the desktop.
The voice calling feature in Telegram works by establishing a direct P2P connection between the users, thereby exchanging data packets between the two directly. Such a connection is said to directly expose the IP addresses of the users. As mentioned, Telegram app users on mobile can choose to prevent their IP addresses from being revealed by changing the settings to Nobody. According to Mishra, this option was absent on Telegram's desktop client. This could result in all calls initiated from the desktop version potentially leaking the users' IP addresses.
Notably, the company has now fixed the issue in the 1.3.17 beta and 1.4 versions of Telegram by adding the Nobody option in its desktop client settings. The IP address leak has received the CVE-2018-17780 vulnerability identifier and as mentioned, the company has rewarded a bounty to Mishra for his bug report. Users can now go to Settings > Privacy and security > Calls > Peer-To-Peer and set the option to Nobody.