Duo push authentications are susceptible to a low-profile timing-based attack that permits an intruder to steal an authenticated session from an end-user accessing Duo-protected resources. Specifically, when multiple push notifications arrive simultaneously (or nearly so), only the final one is shown to the user. When the user authenticates that notification, only the corresponding session will actually be authenticated. If an attacker can initiate an equivalent connection slightly after the client?s session, then the user will typically authorize the malicious session rather than his or her own. Configurations affected include Duo Security Authentication Proxy version 2.4.8 and Duo Win Login version 1.1.8.