A vulnerability in the offline access mode of Cisco Duo Two-Factor Authentication for macOS and Duo Authentication for Windows Logon and RDP could allow an unauthenticated, physical attacker to replay valid user session credentials and gain unauthorized access to an affected macOS or Windows device. This vulnerability exists because session credentials do not properly expire. An attacker could exploit this vulnerability by replaying previously used multifactor authentication (MFA) codes to bypass MFA protection. A successful exploit could allow the attacker to gain unauthorized access to the affected device.