CVE-2026-21909

A Missing Release of Memory after Effective Lifetime vulnerability in the routing protocol daemon (rpd) Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated attacker controlling an adjacent IS-IS neighbor to send a specific update packet causing a memory leak. Continued receipt and processing of these packets will exhaust all available memory, crashing rpd and creating a Denial of Service (DoS) condition.

Memory usage can be monitored through the use of the 'show task memory detail' command. For example:

user@junos> show task memory detail | match ted-infra
  TED-INFRA-COOKIE             25     1072       28     1184       229



user@junos> 

show task memory detail | match ted-infra
  TED-INFRA-COOKIE             31     1360       34     1472       307

This issue affects:

Junos OS: 

  *  from 23.2 before 23.2R2, 
  *  from 23.4 before 23.4R1-S2, 23.4R2, 
  *  from 24.1 before 24.1R2; 


Junos OS Evolved: 

  *  from 23.2 before 23.2R2-EVO, 
  *  from 23.4 before 23.4R1-S2-EVO, 23.4R2-EVO, 
  *  from 24.1 before 24.1R2-EVO.


This issue does not affect Junos OS versions before 23.2R1 or Junos OS Evolved versions before 23.2R1-EVO.