Question: What is CVE-2025-21598?
Answer: CVE-2025-21598 is a vulnerability classified as high with a CVSS score of 8.2. It falls under CWE-125 and affects the system as follows: An Out-of-bounds Read vulnerability in Juniper Networks Junos OS and Junos OS Evolved's routing protocol daemon (rpd) allows an unauthenticated, network-based attacker to send malformed BGP packets to a device configured with packet receive trace options enabled to crash rpd.
This issue affects:

Junos OS: 



  *  from 21.2R3-S8 before 21.2R3-S9, 
  *  from 21.4R3-S7 before 21.4R3-S9, 
  *  from 22.2R3-S4 before 22.2R3-S5, 
  *  from 22.3R3-S2 before 22.3R3-S4, 
  *  from 22.4R3 before 22.4R3-S5, 
  *  from 23.2R2 before 23.2R2-S2, 
  *  from 23.4R1 before 23.4R2-S1, 
  *  from 24.2R1 before 24.2R1-S1, 24.2R2.


Junos OS Evolved:
  *  from 21.4R3-S7-EVO before 21.4R3-S9-EVO, 
  *  from 22.2R3-S4-EVO before 22.2R3-S5-EVO, 
  *  from 22.3R3-S2-EVO before 22.3R3-S4-EVO, 
  *  from 22.4R3-EVO before 22.4R3-S5-EVO, 
  *  from 23.2R2-EVO before 23.2R2-S2-EVO, 
  *  from 23.4R1-EVO before 23.4R2-S1-EVO, 
  *  from 24.2R1-EVO before 24.2R1-S2-EVO, 24.2R2-EVO.


This issue requires a BGP session to be established.

This issue can propagate and multiply through multiple ASes until reaching vulnerable devices.

This issue affects iBGP and eBGP.

This issue affects IPv4 and IPv6.

An indicator of compromise may be the presence of malformed update messages in a neighboring AS which is unaffected by this issue:

For example, by issuing the command on the neighboring device:
 show log messages

Reviewing for similar messages from devices within proximity to each other may indicate this malformed packet is propagating:
  rpd[<pid>]: Received malformed update from <IP address> (External AS <AS#>)
and
  rpd[<pid>]: Malformed Attribute