For the second time in less than a week, users of the popular end-to-end encrypted Signal Desktop messaging app have to update their desktop applications once again to patch another severe code injection vulnerability.
Discovered Monday by the same team of security researchers, the newly discovered vulnerability poses the same threat as the previous one, allowing remote attackers to inject malicious code on the recipients’ Signal desktop app just by sending them a message without requiring any user interaction.
To understand more about the first code injection vulnerability (CVE-2018-10994), you can read our previous article covering how researchers find the Signal flaw and how it works.
The only difference between the two is that the previous flaw resides in the function that handles links shared in the chat, whereas the new vulnerability (CVE-2018-11101) exists in a different function that handles the validation of quoted messages, i.e., quoting a previous message in a reply.
If the victim receives this quoted message containing the malicious payload on its vulnerable Signal desktop app, it will automatically execute the payload, without requiring any user interaction.
Exploiting Signal Code Injection to Steal Plaintext Chats
However, researchers have now managed to craft a new PoC exploit that could allow remote attackers to successfully steal all Signal conversations of the victims in the plaintext just by sending them a message.
This hack literally defeats the purpose of an end-to-end encrypted messaging app, allowing remote attackers to easily get the hold on users’ plain-text conversations without breaking the encryption.
However, the signal app has an auto-update mechanism, so most users must have the update already installed. You can read this guide to ensure if you are running the updated version of Signal.
And if you don’t, you should immediately update your Signal for desktop as soon as possible, since now the vulnerability poses a severe risk of getting your secret conversations exposed in plaintext to attackers and further severe consequences.