A Missing Synchronization vulnerability in the flow collector handler of Juniper Networks Junos OS Evolved on QFX Series allows an adjacent, unauthenticated attacker to cause a Denial-of-Service (DoS).

When the reachability of an sFlow collector changes, the corresponding next-hop entry is updated. If this update occurs simultaneously with the sFlow thread accessing the next-hop data (which is outside the attackers control), it causes the evo-pfemand process to crash, impacting all traffic forwarding until the automatic process restart has completed.

This issue affects Junos OS Evolved on QFX Series:

all 23.2 versions,  23.4 versions before 23.4R2-S7-EVO, 24.2 versions before 24.2R2-S5-EVO, 24.4 versions before 24.4R2-S3-EVO, 25.2 versions before 25.2R2-EVO.