Junos OS: MX Series and SRX Series: The flowd daemon will crash if the SIP ALG is enabled and specific SIP messages are processed

An Improper Locking vulnerability in the SIP ALG of Juniper Networks Junos OS on MX Series and SRX Series allows an unauthenticated networked attacker to cause a flowprocessing daemon (flowd) crash and thereby a Denial of Service (DoS). Continued receipt of these specific packets will cause a sustained Denial of Service condition. This issue can occur in a scenario where the SIP ALG is enabled and specific SIP messages are being processed simultaneously. This issue affects: Juniper Networks Junos OS on MX Series and SRX Series 20.4 versions prior to 20.4R3-S1; 21.1 versions prior to 21.1R2-S2, 21.1R3; 21.2 versions prior to 21.2R1-S2, 21.2R2; 21.3 versions prior to 21.3R1-S1, 21.3R2. This issue does not affect Juniper Networks Junos OS versions prior to 20.4R1.