A virtual private network (VPN) device is described that provides a strict anti-replay mechanism for packets in a group VPN. An example first VPN device includes one or more processors, one or more network interfaces configured to receive a packet having an encryption header that includes a group VPN member identifier association with a second VPN device and a sequence number, wherein the first and second VPN devices are members of a group VPN, a data repository configured to store a window of sequence numbers maintained by the first VPN device for the second VPN device, and a VPN session management module operable by the one or more processors to identify the window of sequence numbers based on the group VPN member identifier, determine whether the sequence number of the header is included in the window of sequence numbers, and process the packet based on the determination.