An Unchecked Error Condition vulnerability in the subscriber management daemon (smgd) of Juniper Networks Junos OS allows an unauthenticated adjacent attacker to cause a crash of and thereby a Denial of Service (DoS). In a subscriber management / broadband edge environment if a single session group configuration contains dual-stack and a pp0 interface smgd will crash and restart every time a PPPoE client sends a specific message. This issue affects Juniper Networks Junos OS on MX Series: 16.1 version 16.1R1 and later versions prior to 18.4R3-S10; 19.1 versions prior to 19.1R2-S3 19.1R3-S7; 19.2 versions prior to 19.2R1-S8 19.2R3-S4; 19.3 versions prior to 19.3R3-S4; 19.4 versions prior to 19.4R3-S5; 20.1 versions prior to 20.1R3-S3; 20.2 versions prior to 20.2R3-S3; 20.3 versions prior to 20.3R3-S2; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R3; 21.2 versions prior to 21.2R2. This issue does not affect Juniper Networks Junos OS versions prior to 16.1R1.