Question: What is CVE-2025-21599?
Answer: CVE-2025-21599 is a vulnerability classified as high with a CVSS score of 8.7. It falls under CWE-401 and affects the system as follows: A Missing Release of Memory after Effective Lifetime vulnerability in the Juniper Tunnel Driver (jtd) of Juniper Networks Junos OS Evolved allows an unauthenticated network-based attacker to cause Denial of Service. 

Receipt of specifically malformed IPv6 packets, destined to the device, causes kernel memory to not be freed, resulting in memory exhaustion leading to a system crash and Denial of Service (DoS). Continuous receipt and processing of these packets will continue to exhaust kernel memory, creating a sustained Denial of Service (DoS) condition.
This issue only affects systems configured with IPv6.

This issue affects Junos OS Evolved: 



  *  from 22.4-EVO before 22.4R3-S5-EVO, 
  *  from 23.2-EVO before 23.2R2-S2-EVO, 
  *  from 23.4-EVO before 23.4R2-S2-EVO, 
  *  from 24.2-EVO before 24.2R1-S2-EVO, 24.2R2-EVO.




This issue does not affect Juniper Networks Junos OS Evolved versions prior to 22.4R1-EVO.