When DNS filtering is enabled on Juniper Networks Junos MX Series with one of the following cards MS-PIC, MS-MIC or MS-MPC, an incoming stream of packets processed by the Multiservices PIC Management Daemon (mspmand) process, responsible for managing "URL Filtering service", may crash, causing the Services PIC to restart. While the Services PIC is restarting, all PIC services including DNS filtering service (DNS sink holing) will be bypassed until the Services PIC completes its boot process. This vulnerability might allow an attacker to cause an extended Denial of Service (DoS) attack against the device and to cause clients to be vulnerable to DNS based attacks by malicious DNS servers when they send DNS requests through the device. As a result, devices which were once protected by the DNS Filtering service are no longer protected and at risk of exploitation.

This issue affects Juniper Networks Junos OS:

• 17.3 versions prior to 17.3R3-S8;
• 18.3 versions prior to 18.3R3-S1;
• 18.4 versions prior to 18.4R3;
• 19.1 versions prior to 19.1R3;
• 19.2 versions prior to 19.2R2;
• 19.3 versions prior to 19.3R3.

This issue does not affect Juniper Networks Junos OS 17.4, 18.1, and 18.2.

The following minimal configuration is required:

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

This issue was seen during production usage.

This issue has been assigned CVE-2020-1660 .

The following software releases have been updated to resolve this specific issue: Junos OS 17.3R3-S8, 18.3R3-S1, 18.4R3, 19.1R3, 19.2R2, 19.3R3, 19.4R1 and all subsequent releases.

This issue is being tracked as 1469188 .

Software releases or updates are available for download at https://www.juniper.net/support/downloads/ .

There are no viable workarounds for this issue.

2020-10-14: Initial Publication.

• KB16613: Overview of the Juniper Networks SIRT Quarterly Security Bulletin Publication Process [juniper.net]
• KB16765: In which releases are vulnerabilities fixed? [juniper.net]
• KB16446: Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories [juniper.net]
• Report a Vulnerability - How to Contact the Juniper Networks Security Incident Response Team
• CVE-2020-1660 at cve.mitre.org