The software patch will be issued by the end of the week.
The bug allows an iPhone user placing a call using Apple's FaceTime video-calling feature to hear audio from the recipient's phone even if the recipient has not yet picked up the call, according to Reuters.
In certain situations, the bug also broadcast both video and audio from the recipient's phone, the technology news website the Verge noted.
Apple's group FaceTime was temporarily made unavailable due to an ongoing issue, according to Apple's system status webpage.
The Cupertino, California-based company was not immediately available to comment on the update on its system status page.
Apple announced the feature last summer, but then removed it from early test versions of its iOS 12 operating system.
The company launched the feature in October.
Apple will report its fiscal first quarter results after the markets close on Tuesday.