An Improper Handling of Exceptional Conditions vulnerability in the Routing Protocol Daemon (RPD) of Juniper Networks Junos OS and Junos OS Evolved allows an attacker sending a specific malformed BGP update message to cause the session to reset, resulting in a Denial of Service (DoS). Continued receipt and processing of these malformed BGP update messages will create a sustained Denial of Service (DoS) condition. Upon receipt of a BGP update message over an established BGP session containing a specifically malformed tunnel encapsulation attribute, when segment routing is enabled, internal processing of the malformed attributes within the update results in improper parsing of remaining attributes, leading to session reset: BGP SEND Notification code 3 (Update Message Error) subcode 1 (invalid attribute list) Only systems with segment routing enabled are vulnerable to this issue. This issue affects eBGP and iBGP, in both IPv4 and IPv6 implementations, and requires a remote attacker to have at least one established BGP session. This issue affects: Junos OS: * All versions before 21.4R3-S8, * from 22.2 before 22.2R3-S4, * from 22.3 before 22.3R3-S3, * from 22.4 before 22.4R3-S3, * from 23.2 before 23.2R2-S1, * from 23.4 before 23.4R1-S2, 23.4R2. Junos OS Evolved:  * All versions before 21.4R3-S8-EVO, * from 22.2-EVO before 22.2R3-S4-EVO, * from 22.3-EVO before 22.3R3-S3-EVO, * from 22.4-EVO before 22.4R3-S3-EVO, * from 23.2-EVO before 23.2R2-S1-EVO, * from 23.4-EVO before 23.4R1-S2-EVO, 23.4R2-EVO.