Gossip spreads fastest in teams with no clear information. Leaders who share updates starve rumors.

Rumors fill vacuums. When people do not know what is happening they do not wait patiently, they build an explanation out of whatever is lying around, and it is almost always worse than the truth. Telling them what you actually know, including the parts still undecided, takes away the raw material.

Pick the thing your team is most uncertain about and say the plain state of it, even if the plain state is that nothing is decided yet. Then come back when you said you would. Most of the whispering stops on its own.