An Improper Handling of Exceptional Conditions vulnerability in AS PATH processing of Juniper Networks Junos OS and Junos OS Evolved allows an attacker to send a BGP update message with an AS PATH containing a large number of 4-byte ASes, leading to a Denial of Service (DoS). Continued receipt and processing of these BGP updates will create a sustained Denial of Service (DoS) condition.

This issue is hit when the router has Non-Stop Routing (NSR) enabled, has a non-4-byte-AS capable BGP neighbor, receives a BGP update message with a prefix that includes a long AS PATH containing large number of 4-byte ASes, and has to advertise the prefix towards the non-4-byte-AS capable BGP neighbor.

Note: NSR is not supported on the SRX Series and is therefore not affected by this vulnerability. This issue affects:

Juniper Networks Junos OS:

• All versions prior to 20.4R3-S8;
• 21.1 versions 21.1R1 and later;
• 21.2 versions prior to 21.2R3-S6;
• 21.3 versions prior to 21.3R3-S5;
• 21.4 versions prior to 21.4R3-S5;
• 22.1 versions prior to 22.1R3-S4;
• 22.2 versions prior to 22.2R3-S2;
• 22.3 versions prior to 22.3R2-S2, 22.3R3-S1;
• 22.4 versions prior to 22.4R2-S1, 22.4R3.

Juniper Networks Junos OS Evolved

• All versions prior to 20.4R3-S8-EVO;
• 21.1 versions 21.1R1-EVO and later;
• 21.2 versions prior to 21.2R3-S6-EVO;
• 21.3 versions prior to 21.3R3-S5-EVO;
• 21.4 versions prior to 21.4R3-S5-EVO;
• 22.1 versions prior to 22.1R3-S4-EVO;
• 22.2 versions prior to 22.2R3-S2-EVO;
• 22.3 versions prior to 22.3R2-S2-EVO, 22.3R3-S1-EVO;
• 22.4 versions prior to 22.4R2-S1-EVO, 22.4R3-EVO.