Google Project Zero researcher Natalie Silvanovich discovered a logical vulnerability in the Signal messaging app for Android that could allow malicious caller to force a call to be answered at the receiver’s end without requiring his/her interaction. Signal security team immediately acknowledged the issue and patched it within a few hours on the same day with the release of Signal for Android v4.47.7. The flaw also affects the iOS version of the messaging app, but can’t be exploited because “the call is not completed due to an error in the UI caused by the unexpected sequence of states”
Source: https://thehackernews.com/2019/10/signal-messenger-bug.html