In a certain condition, receipt of a specific BGP UPDATE message might cause Juniper Networks Junos OS and Junos OS Evolved devices to advertise an invalid BGP UPDATE message to other peers, causing the other peers to terminate the established BGP session, creating a Denial of Service (DoS) condition. For example, Router A sends a specific BGP UPDATE to Router B, causing Router B to send an invalid BGP UPDATE message to Router C, resulting in termination of the BGP session between Router B and Router C. This issue might occur when there is at least a single BGP session established on the device that does not support 4 Byte AS extension (RFC 4893). Repeated receipt of the same BGP UPDATE can result in an extended DoS condition. This issue affects Juniper Networks Junos OS: 16.1 versions prior to 16.1R7-S6; 16.2 versions prior to 16.2R2-S11; 17.1 versions prior to 17.1R2-S11, 17.1R3-S2; 17.2 versions prior to 17.2R1-S9, 17.2R2-S8, 17.2R3-S3; 17.2X75 versions prior to 17.2X75-D105, 17.2X75-D110, 17.2X75-D44; 17.3 versions prior to 17.3R2-S5, 17.3R3-S7; 17.4 versions prior to 17.4R2-S8, 17.4R3; 18.1 versions prior to 18.1R3-S8; 18.2 versions prior to 18.2R2-S6, 18.2R3-S2; 18.2X75 versions prior to 18.2X75-D12, 18.2X75-D33, 18.2X75-D411, 18.2X75-D420, 18.2X75-D51, 18.2X75-D60; 18.3 versions prior to 18.3R1-S6, 18.3R2-S3, 18.3R3; 18.4 versions prior to 18.4R1-S5, 18.4R3; 18.4 version 18.4R2 and later versions; 19.1 versions prior to 19.1R1-S3, 19.1R2; 19.2 versions prior to 19.2R1-S2, 19.2R2. This issue does not affect Juniper Networks Junos OS prior to 16.1R1. This issue affects Juniper Networks Junos OS Evolved prior to 19.2R2-EVO.