Academic researchers have discovered serious vulnerabilities in the core of Threema, an instant messenger that its Switzerland-based developer says provides a level of security and privacy “no other chat service” can offer. Despite the unusually strong claims and two independent security audits Threema has received, the researchers said the flaws completely undermine assurances of confidentiality and authentication that are the cornerstone of any program sold as providing end-to-end encryption, typically abbreviated as E2EE.
Threema has more than 10 million users, which include the Swiss government, the Swiss army, German Chancellor Olaf Scholz, and other politicians in that country. Threema developers advertise it as a more secure alternative to Meta’s WhatsApp messenger. It’s among the top Android apps for a fee-based category in Switzerland, Germany, Austria, Canada, and Australia. The app uses a custom-designed encryption protocol in contravention of established cryptographic norms.
The seven deadly flaws
Researchers from the Zurich-based ETH research university reported on Monday that they found seven vulnerabilities in Threema that seriously call into question the true level of security the app has offered over the years. Two of the vulnerabilities require no special access to a Threema server or app to cryptographically impersonate a user. Three vulnerabilities require an attacker to gain access to a Threema server. The remaining two can be exploited when an attacker gains access to an unlocked phone, such as at a border crossing.