Vulnerability Database

346,508

Total vulnerabilities in the database

CVE-2021-0257 — juniper / junos

Missing Release of Memory after Effective Lifetime

On Juniper Networks MX Series and EX9200 Series platforms with Trio-based MPCs (Modular Port Concentrators) where Integrated Routing and Bridging (IRB) interfaces are configured and mapped to a VPLS instance or a Bridge-Domain, certain Layer 2 network events at Customer Edge (CE) devices may cause memory leaks in the MPC of Provider Edge (PE) devices which can cause an out of memory condition and MPC restart. When this issue occurs, there will be temporary traffic interruption until the MPC is restored. An administrator can use the following CLI command to monitor the status of memory usage level of the MPC: user@device> show system resource-monitor fpc FPC Resource Usage Summary Free Heap Mem Watermark : 20 % Free NH Mem Watermark : 20 % Free Filter Mem Watermark : 20 % * - Watermark reached Slot # % Heap Free RTT Average RTT 1 87 PFE # % ENCAP mem Free % NH mem Free % FW mem Free 0 NA 88 99 1 NA 89 99 When the issue is occurring, the value of “% NH mem Free” will go down until the MPC restarts. This issue affects MX Series and EX9200 Series with Trio-based PFEs (Packet Forwarding Engines), including MX-MPC1-3D, MX-MPC1E-3D, MX-MPC2-3D, MX-MPC2E-3D, MPC-3D-16XGE, and CHAS-MXxx Series MPCs. No other products or platforms are affected by this issue. This issue affects Juniper Networks Junos OS on MX Series, EX9200 Series: 17.3 versions prior to 17.3R3-S10; 17.4 versions prior to 17.4R3-S3; 18.2 versions prior to 18.2R3-S7; 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R3-S6; 19.2 versions prior to 19.2R3-S2; 19.3 versions prior to 19.3R3-S1; 19.4 versions prior to 19.4R2-S2, 19.4R3; 20.2 versions prior to 20.2R1-S3, 20.2R2; 20.3 versions prior to 20.3R1-S1,, 20.3R2. This issue does not affect Juniper Networks Junos OS: 17.3 versions prior to 17.3R3-S8; 17.4 versions prior to 17.4R3-S2; 18.1; 18.2 versions prior to 18.2R3-S4; 18.3 versions prior to 18.3R3-S2; 18.4 versions prior to 18.4R3-S1; 19.1; 19.2 versions prior to 19.2R2; 19.3 versions prior to 19.3R3; 19.4 versions prior to 19.4R2.

  • Published: Apr 22, 2021
  • Updated: Nov 16, 2025
  • CVE: CVE-2021-0257
  • Severity: Medium
  • Exploit:

CVSS v3:

  • Severity: Medium
  • Score: 6.5
  • AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v2:

  • Severity: Low
  • Score: 3.3
  • AV:A/AC:L/Au:N/C:N/I:N/A:P
Software From Fixed in
juniper / junos 17.3-r1 17.3-r1.x
juniper / junos 17.3-r2 17.3-r2.x
juniper / junos 17.3-r2-s2 17.3-r2-s2.x
juniper / junos 17.3-r3 17.3-r3.x
juniper / junos 17.3-r1-s4 17.3-r1-s4.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 17.3 17.3.x
juniper / junos 17.3-r3-s3 17.3-r3-s3.x
juniper / junos 17.3-r3-s4 17.3-r3-s4.x
juniper / junos 17.3-r3-s5 17.3-r3-s5.x
juniper / junos 17.3-r3-s6 17.3-r3-s6.x
juniper / junos 17.3-r2-s3 17.3-r2-s3.x
juniper / junos 17.3-r1-s1 17.3-r1-s1.x
juniper / junos 17.3-r2-s4 17.3-r2-s4.x
juniper / junos 17.3-r3-s7 17.3-r3-s7.x
juniper / junos 17.3-r2-s5 17.3-r2-s5.x
juniper / junos 17.3-r3-s8 17.3-r3-s8.x
juniper / junos 17.3-r3-s9 17.3-r3-s9.x
juniper / junos 17.4-r2-s11 17.4-r2-s11.x
juniper / junos 17.4-r3-s1 17.4-r3-s1.x
juniper / junos 17.4-r2-s9 17.4-r2-s9.x
juniper / junos 17.4-r2-s10 17.4-r2-s10.x
juniper / junos 17.4-r3-s2 17.4-r3-s2.x
juniper / junos 17.4-r2-s8 17.4-r2-s8.x
juniper / junos 17.4-r2-s5 17.4-r2-s5.x
juniper / junos 17.4-r2-s6 17.4-r2-s6.x
juniper / junos 17.4-r2-s7 17.4-r2-s7.x
juniper / junos 17.4-r2-s3 17.4-r2-s3.x
juniper / junos 17.4-r2-s4 17.4-r2-s4.x
juniper / junos 17.4-r1-s6 17.4-r1-s6.x
juniper / junos 17.4-r1-s7 17.4-r1-s7.x
juniper / junos 17.4-r1-s4 17.4-r1-s4.x
juniper / junos 17.4-r3 17.4-r3.x
juniper / junos 17.4-r2-s1 17.4-r2-s1.x
juniper / junos 17.4 17.4.x
juniper / junos 17.4-r1-s5 17.4-r1-s5.x
juniper / junos 17.4-r1-s2 17.4-r1-s2.x
juniper / junos 17.4-r2-s2 17.4-r2-s2.x
juniper / junos 17.4-r1-s1 17.4-r1-s1.x
juniper / junos 17.4-r1-s3 17.4-r1-s3.x
juniper / junos 17.4-r1 17.4-r1.x
juniper / junos 17.4-r2 17.4-r2.x
juniper / junos 18.2-r1 18.2-r1.x
juniper / junos 18.2 18.2.x
juniper / junos 18.2-r2-s1 18.2-r2-s1.x
juniper / junos 18.2-r2-s2 18.2-r2-s2.x
juniper / junos 18.2-r1-s3 18.2-r1-s3.x
juniper / junos 18.2-r2-s5 18.2-r2-s5.x
juniper / junos 18.2-r2-s6 18.2-r2-s6.x
juniper / junos 18.2-r2-s3 18.2-r2-s3.x
juniper / junos 18.2-r2-s4 18.2-r2-s4.x
juniper / junos 18.2-r1-s4 18.2-r1-s4.x
juniper / junos 18.2-r1-s5 18.2-r1-s5.x
juniper / junos 18.2-r2 18.2-r2.x
juniper / junos 18.2-r3 18.2-r3.x
juniper / junos 18.2-r3-s1 18.2-r3-s1.x
juniper / junos 18.2-r3-s2 18.2-r3-s2.x
juniper / junos 18.2-r3-s3 18.2-r3-s3.x
juniper / junos 18.2-r2-s7 18.2-r2-s7.x
juniper / junos 18.2-r1-s2 18.2-r1-s2.x
juniper / junos 18.3-r3-s3 18.3-r3-s3.x
juniper / junos 18.3-r2-s4 18.3-r2-s4.x
juniper / junos 18.3-r3-s2 18.3-r3-s2.x
juniper / junos 18.3-r3-s1 18.3-r3-s1.x
juniper / junos 18.3-r2-s3 18.3-r2-s3.x
juniper / junos 18.3-r1-s6 18.3-r1-s6.x
juniper / junos 18.3-r3 18.3-r3.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 18.3-r1-s5 18.3-r1-s5.x
juniper / junos 18.3-r1-s4 18.3-r1-s4.x
juniper / junos 18.3-r1-s1 18.3-r1-s1.x
juniper / junos 18.3-r2 18.3-r2.x
juniper / junos 18.3-r1 18.3-r1.x
juniper / junos 18.3-r1-s2 18.3-r1-s2.x
juniper / junos 18.3 18.3.x
juniper / junos 18.3-r1-s3 18.3-r1-s3.x
juniper / junos 18.4-r1-s1 18.4-r1-s1.x
juniper / junos 18.4 18.4.x
juniper / junos 18.4-r1 18.4-r1.x
juniper / junos 18.4-r1-s3 18.4-r1-s3.x
juniper / junos 18.4-r1-s4 18.4-r1-s4.x
juniper / junos 18.4-r1-s2 18.4-r1-s2.x
juniper / junos 18.4-r1-s5 18.4-r1-s5.x
juniper / junos 18.4-r2 18.4-r2.x
juniper / junos 18.4-r2-s1 18.4-r2-s1.x
juniper / junos 18.4-r2-s2 18.4-r2-s2.x
juniper / junos 18.4-r3 18.4-r3.x
juniper / junos 18.4-r2-s3 18.4-r2-s3.x
juniper / junos 18.4-r1-s6 18.4-r1-s6.x
juniper / junos 18.4-r3-s2 18.4-r3-s2.x
juniper / junos 18.4-r3-s1 18.4-r3-s1.x
juniper / junos 18.4-r2-s4 18.4-r2-s4.x
juniper / junos 18.4-r3-s3 18.4-r3-s3.x
juniper / junos 18.4-r3-s4 18.4-r3-s4.x
juniper / junos 18.4-r3-s5 18.4-r3-s5.x
juniper / junos 18.4-r2-s5 18.4-r2-s5.x
juniper / junos 18.4-r2-s6 18.4-r2-s6.x
juniper / junos 18.4-r1-s7 18.4-r1-s7.x
juniper / junos 19.2-r2-s1 19.2-r2-s1.x
juniper / junos 19.2-r3-s1 19.2-r3-s1.x
juniper / junos 19.2-r3 19.2-r3.x
juniper / junos 19.2-r1-s5 19.2-r1-s5.x
juniper / junos 19.2-r2 19.2-r2.x
juniper / junos 19.2-r1-s4 19.2-r1-s4.x
juniper / junos 19.2 19.2.x
juniper / junos 19.2-r1-s3 19.2-r1-s3.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 19.2-r1 19.2-r1.x
juniper / junos 19.3 19.3.x
juniper / junos 19.3-r1 19.3-r1.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 19.3-r2.x
juniper / junos 19.3-r2-s2 19.3-r2-s2.x
juniper / junos 19.3-r2-s4 19.3-r2-s4.x
juniper / junos 19.3-r2-s3 19.3-r2-s3.x
juniper / junos 19.3-r2-s5 19.3-r2-s5.x
juniper / junos 19.3-r3 19.3-r3.x
juniper / junos 19.4-r2 19.4-r2.x
juniper / junos 19.4-r2-s1 19.4-r2-s1.x
juniper / junos 19.4-r1-s2 19.4-r1-s2.x
juniper / junos 19.4-r1-s1 19.4-r1-s1.x
juniper / junos 19.4-r1 19.4-r1.x
juniper / junos 20.2-r1 20.2-r1.x
juniper / junos 20.2-r1-s1 20.2-r1-s1.x
juniper / junos 20.2-r1-s2 20.2-r1-s2.x
juniper / junos 20.3-r1 20.3-r1.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.