A Stack-based Buffer Overflow vulnerability in Flow Processing Daemon (flowd) of Juniper Networks Junos OS allows an unauthenticated, network-based attacker to cause Denial of Service (DoS). On all Junos OS MX Series platforms with SPC3 and MS-MPC/-MIC, when URL filtering is enabled and a specific URL request is received and processed, flowd will crash and restart. Continuous reception of the specific URL request will lead to a sustained Denial of Service (DoS) condition. This issue affects: Junos OS: * all versions before 21.2R3-S6, * from 21.3 before 21.3R3-S5, * from 21.4 before 21.4R3-S5, * from 22.1 before 22.1R3-S3, * from 22.2 before 22.2R3-S1, * from 22.3 before 22.3R2-S2, 22.3R3, * from 22.4 before 22.4R2-S1, 22.4R3.