On MX Series, when the SIP ALG is enabled, receipt of a certain malformed SIP packet may crash the MS-PIC component on MS-MIC or MS-MPC. By continuously sending a crafted SIP packet, an attacker can repeatedly bring down MS-PIC on MS-MIC/MS-MPC causing a sustained Denial of Service. This issue affects Juniper Networks Junos OS on MX Series: 16.1 versions prior to 16.1R7-S5; 16.2 versions prior to 16.2R2-S11; 17.1 versions prior to 17.1R3; 17.2 versions prior to 17.2R3-S3; 17.3 versions prior to 17.3R3-S6 ; 17.4 versions prior to 17.4R2-S8, 17.4R3; 18.1 versions prior to 18.1R3-S3; 18.2 versions prior to 18.2R3; 18.3 versions prior to 18.3R2; 18.4 versions prior to 18.4R2.