CVE-2020-1665: On Juniper Networks MX Series and EX9200 Series, in a certain condition the IPv6 Distributed Denial of Service (DDoS) protection might not take affect...

Description

On Juniper Networks MX Series and EX9200 Series, in a certain condition the IPv6 Distributed Denial of Service (DDoS) protection might not take affect when it reaches the threshold condition. The DDoS protection allows the device to continue to function while it is under DDoS attack, protecting both the Routing Engine (RE) and the Flexible PIC Concentrator (FPC) during the DDoS attack. When this issue occurs, the RE and/or the FPC can become overwhelmed, which could disrupt network protocol operations and/or interrupt traffic. This issue does not affect IPv4 DDoS protection. This issue affects MX Series and EX9200 Series with Trio-based PFEs (Packet Forwarding Engines). Please refer to https://kb.juniper.net/KB25385 for the list of Trio-based PFEs. This issue affects Juniper Networks Junos OS on MX series and EX9200 Series: 17.2 versions prior to 17.2R3-S4; 17.2X75 versions prior to 17.2X75-D102, 17.2X75-D110; 17.3 versions prior to 17.3R3-S8; 17.4 versions prior to 17.4R2-S11, 17.4R3-S2; 18.2 versions prior to 18.2R2-S7, 18.2R3, 18.2R3-S3; 18.2X75 versions prior to 18.2X75-D30; 18.3 versions prior to 18.3R2-S4, 18.3R3-S2.

Metrics

CVSS 3.1

5.3/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS Probability

1.26%

66.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-794

Affected Software

Vendor	Product	Versions
Juniper	Junos	17.2
Juniper	Junos	17.2x75
Juniper	Junos	17.3
Juniper	Junos	17.4
Juniper	Junos	18.2
Juniper	Junos	18.2x75
Juniper	Junos	18.3

References

https://kb.juniper.net/JSA11062Vendor Advisory
https://kb.juniper.net/KB25385Vendor Advisory
https://kb.juniper.net/JSA11062Vendor Advisory
https://kb.juniper.net/KB25385Vendor Advisory

Timeline

Published: Oct 16, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-1665?

On Juniper Networks MX Series and EX9200 Series, in a certain condition the IPv6 Distributed Denial of Service (DDoS) protection might not take affect when it reaches the threshold condition. The DDoS protection allows the device to continue to function while it is under DDoS attack, protecting both the Routing Engine (RE) and the Flexible PIC Concentrator (FPC) during the DDoS attack. When this issue occurs, the RE and/or the FPC can become overwhelmed, which could disrupt network protocol operations and/or interrupt traffic. This issue does not affect IPv4 DDoS protection. This issue affects MX Series and EX9200 Series with Trio-based PFEs (Packet Forwarding Engines). Please refer to https://kb.juniper.net/KB25385 for the list of Trio-based PFEs. This issue affects Juniper Networks Junos OS on MX series and EX9200 Series: 17.2 versions prior to 17.2R3-S4; 17.2X75 versions prior to 17.2X75-D102, 17.2X75-D110; 17.3 versions prior to 17.3R3-S8; 17.4 versions prior to 17.4R2-S11, 17.4R3-S2; 18.2 versions prior to 18.2R2-S7, 18.2R3, 18.2R3-S3; 18.2X75 versions prior to 18.2X75-D30; 18.3 versions prior to 18.3R2-S4, 18.3R3-S2.

How severe is CVE-2020-1665?

CVE-2020-1665 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 1.26% probability of exploitation in the next 30 days.

How do I fix CVE-2020-1665?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.