Vulnerability Database

346,508

Total vulnerabilities in the database

CVE-2020-1660 — juniper / junos

Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

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.

  • Published: Oct 16, 2020
  • Updated: Nov 16, 2025
  • CVE: CVE-2020-1660
  • Severity: High
  • Exploit:

CVSS v3:

  • Severity: High
  • Score: 8.3
  • AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L

CVSS v2:

  • Severity: Medium
  • Score: 6.8
  • AV:N/AC:M/Au:N/C:P/I:P/A:P

CWEs:

Software From Fixed in
juniper / junos 17.3-r2 17.3-r2.x
juniper / junos 17.3-r2-s2 17.3-r2-s2.x
juniper / junos 18.3-r1-s1 18.3-r1-s1.x
juniper / junos 17.3-r3-s1 17.3-r3-s1.x
juniper / junos 17.3-r3-s2 17.3-r3-s2.x
juniper / junos 17.3-r2-s1 17.3-r2-s1.x
juniper / junos 18.3-r2 18.3-r2.x
juniper / junos 18.3-r1 18.3-r1.x
juniper / junos 18.4-r1 18.4-r1.x
juniper / junos 17.3 17.3.x
juniper / junos 18.3-r1-s2 18.3-r1-s2.x
juniper / junos 18.3 18.3.x
juniper / junos 18.4 18.4.x
juniper / junos 17.3-r3 17.3-r3.x
juniper / junos 17.3-r3-s3 17.3-r3-s3.x
juniper / junos 18.4-r1-s1 18.4-r1-s1.x
juniper / junos 17.3-r3-s4 17.3-r3-s4.x
juniper / junos 18.3-r1-s3 18.3-r1-s3.x
juniper / junos 18.4-r1-s2 18.4-r1-s2.x
juniper / junos 19.1-r1 19.1-r1.x
juniper / junos 19.1 19.1.x
juniper / junos 17.3-r2-s3 17.3-r2-s3.x
juniper / junos 19.2-r1 19.2-r1.x
juniper / junos 18.4-r2 18.4-r2.x
juniper / junos 19.1-r1-s1 19.1-r1-s1.x
juniper / junos 19.1-r1-s3 19.1-r1-s3.x
juniper / junos 19.1-r1-s2 19.1-r1-s2.x
juniper / junos 17.3-r1-s1 17.3-r1-s1.x
juniper / junos 18.4-r1-s5 18.4-r1-s5.x
juniper / junos 19.2-r1-s1 19.2-r1-s1.x
juniper / junos 19.2-r1-s2 19.2-r1-s2.x
juniper / junos 18.3-r1-s5 18.3-r1-s5.x
juniper / junos 17.3-r2-s4 17.3-r2-s4.x
juniper / junos 18.3-r2-s1 18.3-r2-s1.x
juniper / junos 18.3-r2-s2 18.3-r2-s2.x
juniper / junos 18.4-r2-s1 18.4-r2-s1.x
juniper / junos 19.3 19.3.x
juniper / junos 19.3-r1 19.3-r1.x
juniper / junos 19.2 19.2.x
juniper / junos 18.4-r2-s2 18.4-r2-s2.x
juniper / junos 18.3-r1-s6 18.3-r1-s6.x
juniper / junos 19.2-r1-s3 19.2-r1-s3.x
juniper / junos 18.3-r3 18.3-r3.x
juniper / junos 19.3-r2 19.3-r2.x
juniper / junos 19.1-r2 19.1-r2.x
juniper / junos 18.4-r2-s3 18.4-r2-s3.x
juniper / junos 17.3-r3-s7 17.3-r3-s7.x
juniper / junos 19.3-r2-s1 19.3-r2-s1.x
juniper / junos 19.3-r1-s1 19.3-r1-s1.x
juniper / junos 19.3-r2-s2 19.3-r2-s2.x
juniper / junos 19.1-r1-s4 19.1-r1-s4.x
juniper / junos 18.4-r1-s6 18.4-r1-s6.x
juniper / junos 18.3-r2-s3 18.3-r2-s3.x
juniper / junos 17.3-r2-s5 17.3-r2-s5.x
juniper / junos 18.4-r2-s4 18.4-r2-s4.x
juniper / junos 19.1-r2-s1 19.1-r2-s1.x

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.