CVE-2025-21594

Junos OS: MX Series: In DS-lite and NAT scenario receipt of crafted IPv6 traffic causes port block

Published Apr 9, 2025 CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
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.

Remediation

Vendor Solution

The following software releases have been updated to resolve this specific issue: Junos OS: 21.2R3-S8, 21.4R3-S7, 22.1R3-S6, 22.2R3-S4, 22.3R3-S3, 22.4R3-S2, 23.2R2-S1, 23.4R1-S2, 23.4R2, 24.2R1, and all subsequent releases.


Vendor Workaround

Modify the IPv6 prefix-length to be 64/96/128 through the command: [ set services service-set <*> softwire-options dslite-ipv6-prefix-length 64/96/128]

Tracking

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Advisories

Source ID Title
EUVD EUVD EUVD-2025-10531 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.
References
History
Type Values Removed Values Added
First Time appeared Juniper
Juniper junos
Juniper mx10004
Juniper mx10008
Juniper mx2008
Juniper mx2010
Juniper mx2020
Juniper mx204
Juniper mx240
Juniper mx304
Juniper mx480
Juniper mx960
CPEs cpe:2.3:h:juniper:mx10004:-:*:*:*:*:*:*:*
cpe:2.3:h:juniper:mx10008:-:*:*:*:*:*:*:*
cpe:2.3:h:juniper:mx2008:-:*:*:*:*:*:*:*
cpe:2.3:h:juniper:mx2010:-:*:*:*:*:*:*:*
cpe:2.3:h:juniper:mx2020:-:*:*:*:*:*:*:*
cpe:2.3:h:juniper:mx204:-:*:*:*:*:*:*:*
cpe:2.3:h:juniper:mx240:-:*:*:*:*:*:*:*
cpe:2.3:h:juniper:mx304:-:*:*:*:*:*:*:*
cpe:2.3:h:juniper:mx480:-:*:*:*:*:*:*:*
cpe:2.3:h:juniper:mx960:-:*:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r2-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r2-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s4:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s5:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s6:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s7:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:r2-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:r2-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:r3-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:r3-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:r3-s3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:r3-s4:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:r3-s5:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:r3-s6:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.4:r3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.1:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.1:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.1:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.1:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.1:r2-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.1:r2-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.1:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.1:r3-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.1:r3-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.1:r3-s3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.1:r3-s4:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.1:r3-s5:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.1:r3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.2:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.2:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.2:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.2:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.2:r2-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.2:r2-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.2:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.2:r3-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.2:r3-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.2:r3-s3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.2:r3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.3:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.3:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.3:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.3:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.3:r2-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.3:r2-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.3:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.3:r3-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.3:r3-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.3:r3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r2-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r2-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r3-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:22.4:r3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.2:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.2:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.2:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.2:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.2:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.4:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.4:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.4:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.4:r2:*:*:*:*:*:*
Vendors & Products Juniper
Juniper junos
Juniper mx10004
Juniper mx10008
Juniper mx2008
Juniper mx2010
Juniper mx2020
Juniper mx204
Juniper mx240
Juniper mx304
Juniper mx480
Juniper mx960
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

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

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/R:U'}