Juniper Junos OS: 2024-07 Security Bulletin: Junos OS: SRX4600, SRX5000 Series: TCP packets with SYN/FIN or SYN/RST are transferred after enabling no-syn-check with Express Path (JSA83021) (CVE-2024-39561)

An Improper Check for Unusual or Exceptional Conditions vulnerability in the flow daemon (flowd) of Juniper Networks Junos OS on

SRX4600 and SRX5000 Series

allows an attacker to send TCP packets with

SYN/FIN or SYN/RST

flags, bypassing the expected blocking of these packets.

A TCP packet with SYN/FIN or SYN/RST should be dropped in flowd. However, when no-syn-check and Express Path are enabled, these TCP packets are unexpectedly transferred to the downstream network.

This issue affects Junos OS on SRX4600 and SRX5000 Series:

* All versions before 21.2R3-S8,
* from 21.4 before 21.4R3-S7,
* from 22.1 before 22.1R3-S6,
* from 22.2 before 22.2R3-S4,
* from 22.3 before 22.3R3-S3,
* from 22.4 before 22.4R3-S2,
* from 23.2 before 23.2R2,
* from 23.4 before 23.4R1-S1, 23.4R2.