An Improper Check for Unusual or Exceptional Conditions vulnerability in the pfe (packet forwarding engine) of Juniper Networks Junos OS on MX Series causes a port within a pool to be blocked leading to Denial of Service (DoS).
In a DS-Lite (Dual-Stack Lite) and NAT (Network Address Translation) scenario, when crafted IPv6 traffic is received and prefix-length is set to 56, the ports assigned to the user will not be freed.  Eventually, users cannot establish new connections. Affected FPC/PIC need to be manually restarted to recover.
Following is the command to identify the issue: 
    user@host> show services nat source port-block 
    Host_IP                       External_IP                    Port_Block      Ports_Used/        Block_State/
                                                               Range             Ports_Total        Left_Time(s)
    2001::                        x.x.x.x                     58880-59391     256/256*1         Active/-        >>>>>>>>port still usedThis issue affects Junos OS on MX Series: 
  *  from 21.2 before 21.2R3-S8, 
  *  from 21.4 before 21.4R3-S7, 
  *  from 22.1 before 22.1R3-S6, 
  *  from 22.2 before 22.2R3-S4, 
  *  from 22.3 before 22.3R3-S3, 
  *  from 22.4 before 22.4R3-S2, 
  *  from 23.2 before 23.2R2-S1, 
  *  from 23.4 before 23.4R1-S2, 23.4R2.
This issue does not affect versions before 20.2R1.
                
            Metrics
Affected Vendors & Products
References
        | Link | Providers | 
|---|---|
| https://supportportal.juniper.net/JSA96449 |     | 
History
                    Thu, 10 Apr 2025 14:15:00 +0000
| Type | Values Removed | Values Added | 
|---|---|---|
| Metrics | ssvc 
 | 
Wed, 09 Apr 2025 20:00:00 +0000
| Type | Values Removed | Values Added | 
|---|---|---|
| Description | An Improper Check for Unusual or Exceptional Conditions vulnerability in the pfe (packet forwarding engine) of Juniper Networks Junos OS on MX Series causes a port within a pool to be blocked leading to Denial of Service (DoS). In a DS-Lite (Dual-Stack Lite) and NAT (Network Address Translation) scenario, when crafted IPv6 traffic is received and prefix-length is set to 56, the ports assigned to the user will not be freed. Eventually, users cannot establish new connections. Affected FPC/PIC need to be manually restarted to recover. Following is the command to identify the issue: user@host> show services nat source port-block Host_IP External_IP Port_Block Ports_Used/ Block_State/ Range Ports_Total Left_Time(s) 2001:: x.x.x.x 58880-59391 256/256*1 Active/- >>>>>>>>port still usedThis issue affects Junos OS on MX Series: * from 21.2 before 21.2R3-S8, * from 21.4 before 21.4R3-S7, * from 22.1 before 22.1R3-S6, * from 22.2 before 22.2R3-S4, * from 22.3 before 22.3R3-S3, * from 22.4 before 22.4R3-S2, * from 23.2 before 23.2R2-S1, * from 23.4 before 23.4R1-S2, 23.4R2. This issue does not affect versions before 20.2R1. | |
| Title | Junos OS: MX Series: In DS-lite and NAT scenario receipt of crafted IPv6 traffic causes port block | |
| Weaknesses | CWE-754 | |
| References |  | |
| Metrics | cvssV3_1 
 
 | 
 MITRE
                        MITRE
                    Status: PUBLISHED
Assigner: juniper
Published: 2025-04-09T19:49:41.391Z
Updated: 2025-04-10T13:14:00.650Z
Reserved: 2024-12-26T14:47:11.669Z
Link: CVE-2025-21594
 Vulnrichment
                        Vulnrichment
                    Updated: 2025-04-10T13:13:56.855Z
 NVD
                        NVD
                    Status : Awaiting Analysis
Published: 2025-04-09T20:15:25.620
Modified: 2025-04-11T15:40:10.277
Link: CVE-2025-21594
 Redhat
                        Redhat
                    No data.
 ReportizFlow
ReportizFlow