CVE-2020-1638: The FPC (Flexible PIC Concentrator) of Juniper Networks Junos OS and Junos OS Evolved may restart after processing a specific IPv4 packet. Only packet...

Description

The FPC (Flexible PIC Concentrator) of Juniper Networks Junos OS and Junos OS Evolved may restart after processing a specific IPv4 packet. Only packets destined to the device itself, successfully reaching the RE through existing edge and control plane filtering, will be able to cause the FPC restart. When this issue occurs, all traffic via the FPC will be dropped. By continuously sending this specific IPv4 packet, an attacker can repeatedly crash the FPC, causing an extended Denial of Service (DoS) condition. This issue can only occur when processing a specific IPv4 packet. IPv6 packets cannot trigger this issue. This issue affects: Juniper Networks Junos OS on MX Series with MPC10E or MPC11E and PTX10001: 19.2 versions prior to 19.2R1-S4, 19.2R2; 19.3 versions prior to 19.3R2-S2, 19.3R3; 19.4 versions prior to 19.4R1-S1, 19.4R2. Juniper Networks Junos OS Evolved on on QFX5220, and PTX10003 series: 19.2-EVO versions; 19.3-EVO versions; 19.4-EVO versions prior to 19.4R2-EVO. This issue does not affect Junos OS versions prior to 19.2R1. This issue does not affect Junos OS Evolved versions prior to 19.2R1-EVO.

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

1.29%

66.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-467

Affected Software

Vendor	Product	Versions	Update
Juniper	Junos	19.2	—
Juniper	Junos	19.3	R1
Juniper	Junos	19.4	R1
Juniper	Junos Os Evolved	19.2	R1
Juniper	Junos Os Evolved	19.3	R2
Juniper	Junos Os Evolved	19.4	R1

References

https://kb.juniper.net/JSA11019Vendor Advisory
https://kb.juniper.net/JSA11019Vendor Advisory

Timeline

Published: Apr 8, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-1638?

The FPC (Flexible PIC Concentrator) of Juniper Networks Junos OS and Junos OS Evolved may restart after processing a specific IPv4 packet. Only packets destined to the device itself, successfully reaching the RE through existing edge and control plane filtering, will be able to cause the FPC restart. When this issue occurs, all traffic via the FPC will be dropped. By continuously sending this specific IPv4 packet, an attacker can repeatedly crash the FPC, causing an extended Denial of Service (DoS) condition. This issue can only occur when processing a specific IPv4 packet. IPv6 packets cannot trigger this issue. This issue affects: Juniper Networks Junos OS on MX Series with MPC10E or MPC11E and PTX10001: 19.2 versions prior to 19.2R1-S4, 19.2R2; 19.3 versions prior to 19.3R2-S2, 19.3R3; 19.4 versions prior to 19.4R1-S1, 19.4R2. Juniper Networks Junos OS Evolved on on QFX5220, and PTX10003 series: 19.2-EVO versions; 19.3-EVO versions; 19.4-EVO versions prior to 19.4R2-EVO. This issue does not affect Junos OS versions prior to 19.2R1. This issue does not affect Junos OS Evolved versions prior to 19.2R1-EVO.

How severe is CVE-2020-1638?

CVE-2020-1638 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.29% probability of exploitation in the next 30 days.

How do I fix CVE-2020-1638?

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.