An attacker can crash the flowd process causing a DoS.
New builds of Junos OS software are available from Juniper. As a workaround disable ALGs if they are not required or enable flow-based processing for IPv6 traffic.
On SRX Series devices, when any ALG is enabled, a certain crafted packet may cause the flowd process to crash.
Junos OS 11.4, 12.1
Check the OS build.