A Missing Authentication for Critical Function vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS on MX Series with SPC3, and SRX Series allows an unauthenticated network-based attacker to cause limited impact to the integrity or availability of the device. If a device is configured with IPsec authentication algorithm hmac-sha-384 or hmac-sha-512, tunnels are established normally but for traffic traversing the tunnel no authentication information is sent with the encrypted data on egress, and no authentication information is expected on ingress. So if the peer is an unaffected device transit traffic is going to fail in both directions.

If the peer is an also affected device transit traffic works, but without authentication, and configuration and CLI operational commands indicate authentication is performed. This issue affects Junos OS: All versions before 20.4R3-S7, 21.1 versions before 21.1R3, 21.2 versions before 21.2R2-S1, 21.2R3, 21.3 versions before 21.3R1-S2, 21.3R2.