Vulnerability Database

346,508

Total vulnerabilities in the database

CVE-2021-0277 — juniper / junos

Out-of-bounds Read

An Out-of-bounds Read vulnerability in the processing of specially crafted LLDP frames by the Layer 2 Control Protocol Daemon (l2cpd) of Juniper Networks Junos OS and Junos OS Evolved may allow an attacker to cause a Denial of Service (DoS), or may lead to remote code execution (RCE). Continued receipt and processing of these frames, sent from the local broadcast domain, will repeatedly crash the l2cpd process and sustain the Denial of Service (DoS) condition. This issue affects: Juniper Networks Junos OS: 12.3 versions prior to 12.3R12-S18; 15.1 versions prior to 15.1R7-S9; 17.3 versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R2-S13, 17.4R3-S5; 18.1 versions prior to 18.1R3-S13; 18.2 versions prior to 18.2R3-S8; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R2-S8, 18.4R3-S8; 19.1 versions prior to 19.1R3-S5; 19.2 versions prior to 19.2R3-S3; 19.3 versions prior to 19.3R2-S6, 19.3R3-S2; 19.4 versions prior to 19.4R1-S4, 19.4R2-S4, 19.4R3-S3; 20.1 versions prior to 20.1R2-S2, 20.1R3; 20.2 versions prior to 20.2R3-S1; 20.3 versions prior to 20.3R2-S1, 20.3R3; 20.4 versions prior to 20.4R2. Juniper Networks Junos OS Evolved versions prior to 20.4R2-EVO.

  • Published: Jul 15, 2021
  • Updated: Nov 16, 2025
  • CVE: CVE-2021-0277
  • Severity: High
  • Exploit:

CVSS v3:

  • Severity: High
  • Score: 8.8
  • AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v2:

  • Severity: Medium
  • Score: 5.8
  • AV:A/AC:L/Au:N/C:P/I:P/A:P

CWEs:

Software From Fixed in
juniper / junos 15.1-r7 15.1-r7.x
juniper / junos 12.3-r11 12.3-r11.x
juniper / junos 15.1-f1 15.1-f1.x
juniper / junos 15.1-f6-s4 15.1-f6-s4.x
juniper / junos 15.1-f2-s3 15.1-f2-s3.x
juniper / junos 15.1-f7 15.1-f7.x
juniper / junos 15.1-r3 15.1-r3.x
juniper / junos 15.1-r 15.1-r.x
juniper / junos 15.1-f2-s2 15.1-f2-s2.x
juniper / junos 12.3-r1 12.3-r1.x
juniper / junos 15.1-r6 15.1-r6.x
juniper / junos 15.1-f4 15.1-f4.x
juniper / junos 15.1-r4 15.1-r4.x
juniper / junos 15.1-f2-s4 15.1-f2-s4.x
juniper / junos 15.1-f5-s7 15.1-f5-s7.x
juniper / junos 15.1-f6-s7 15.1-f6-s7.x
juniper / junos 15.1-f6 15.1-f6.x
juniper / junos 12.3-r12 12.3-r12.x
juniper / junos 15.1-f2 15.1-f2.x
juniper / junos 15.1-a1 15.1-a1.x
juniper / junos 15.1-f3 15.1-f3.x
juniper / junos 15.1-r2 15.1-r2.x
juniper / junos 15.1-r4-s7 15.1-r4-s7.x
juniper / junos 12.3-r10 12.3-r10.x
juniper / junos 15.1-r4-s8 15.1-r4-s8.x
juniper / junos 15.1-r5-s5 15.1-r5-s5.x
juniper / junos 15.1-r6-s1 15.1-r6-s1.x
juniper / junos 15.1-r5 15.1-r5.x
juniper / junos 15.1-r1 15.1-r1.x
juniper / junos 15.1-f2-s1 15.1-f2-s1.x
juniper / junos 15.1-r5-s1 15.1-r5-s1.x
juniper / junos 15.1-f5 15.1-f5.x
juniper / junos 15.1-f6-s8 15.1-f6-s8.x
juniper / junos 15.1-r5-s3 15.1-r5-s3.x
juniper / junos 17.3-r1 17.3-r1.x
juniper / junos 15.1-r5-s6 15.1-r5-s6.x
juniper / junos 15.1-r6-s2 15.1-r6-s2.x
juniper / junos 15.1-r6-s3 15.1-r6-s3.x
juniper / junos 15.1-r6-s4 15.1-r6-s4.x
juniper / junos 15.1-f6-s9 15.1-f6-s9.x
juniper / junos 15.1-r4-s9 15.1-r4-s9.x
juniper / junos 15.1-r6-s6 15.1-r6-s6.x
juniper / junos 17.3-r2 17.3-r2.x
juniper / junos 17.4-r1 17.4-r1.x
juniper / junos 17.4-r2 17.4-r2.x
juniper / junos 15.1-f 15.1-f.x
juniper / junos 17.3-r2-s2 17.3-r2-s2.x
juniper / junos 17.3-r3 17.3-r3.x
juniper / junos 18.1-r1 18.1-r1.x
juniper / junos 15.1-f6-s3 15.1-f6-s3.x
juniper / junos 18.1-r3 18.1-r3.x
juniper / junos 15.1-r7-s1 15.1-r7-s1.x
juniper / junos 12.3-r12-s10 12.3-r12-s10.x
juniper / junos 15.1-f6-s10 15.1-f6-s10.x
juniper / junos 17.3-r1-s4 17.3-r1-s4.x
juniper / junos 17.4-r1-s3 17.4-r1-s3.x
juniper / junos 18.1-r2 18.1-r2.x
juniper / junos 18.2-r1 18.2-r1.x
juniper / junos 15.1-r7-s2 15.1-r7-s2.x
juniper / junos 15.1-r7-s3 15.1-r7-s3.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 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 17.3-r3-s1 17.3-r3-s1.x
juniper / junos 17.3-r3-s2 17.3-r3-s2.x
juniper / junos 17.4-r1-s2 17.4-r1-s2.x
juniper / junos 17.3-r2-s1 17.3-r2-s1.x
juniper / junos 17.4-r3 17.4-r3.x
juniper / junos 17.4-r2-s1 17.4-r2-s1.x
juniper / junos 18.1-r2-s2 18.1-r2-s2.x
juniper / junos 15.1-f6-s2 15.1-f6-s2.x
juniper / junos 15.1-f6-s1 15.1-f6-s1.x
juniper / junos 15.1-f6-s5 15.1-f6-s5.x
juniper / junos 15.1-f6-s6 15.1-f6-s6.x
juniper / junos 18.4-r1 18.4-r1.x
juniper / junos 17.4 17.4.x
juniper / junos 18.1-r3-s4 18.1-r3-s4.x
juniper / junos 18.1-r3-s3 18.1-r3-s3.x
juniper / junos 18.1-r3-s2 18.1-r3-s2.x
juniper / junos 18.1 18.1.x
juniper / junos 18.1-r2-s1 18.1-r2-s1.x
juniper / junos 18.1-r2-s4 18.1-r2-s4.x
juniper / junos 15.1 15.1.x
juniper / junos 17.3 17.3.x
juniper / junos 12.3-r12-s8 12.3-r12-s8.x
juniper / junos 18.4 18.4.x
juniper / junos 17.4-r1-s5 17.4-r1-s5.x
juniper / junos 18.1-r3-s1 18.1-r3-s1.x
juniper / junos 17.3-r3-s3 17.3-r3-s3.x
juniper / junos 17.4-r1-s7 17.4-r1-s7.x
juniper / junos 12.3 12.3.x
juniper / junos 17.4-r1-s4 17.4-r1-s4.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 17.3-r3-s5 17.3-r3-s5.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 18.1-r3-s5 18.1-r3-s5.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 17.3-r3-s6 17.3-r3-s6.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 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 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 19.2-r1 19.2-r1.x
juniper / junos 18.4-r2 18.4-r2.x
juniper / junos 18.2-r3 18.2-r3.x
juniper / junos 18.1-r3-s6 18.1-r3-s6.x
juniper / junos 18.1-r3-s7 18.1-r3-s7.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 12.3-r12-s13 12.3-r12-s13.x
juniper / junos 12.3-r12-s14 12.3-r12-s14.x
juniper / junos 15.1-r7-s4 15.1-r7-s4.x
juniper / junos 17.3-r1-s1 17.3-r1-s1.x
juniper / junos 15.1-r7-s5 15.1-r7-s5.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 18.4-r1-s5 18.4-r1-s5.x
juniper / junos 15.1-f6-s12 15.1-f6-s12.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 18.2-r3-s1 18.2-r3-s1.x
juniper / junos 12.3-r12-s1 12.3-r12-s1.x
juniper / junos 12.3-r12-s3 12.3-r12-s3.x
juniper / junos 12.3-r12-s4 12.3-r12-s4.x
juniper / junos 12.3-r12-s6 12.3-r12-s6.x
juniper / junos 12.3-r12-s11 12.3-r12-s11.x
juniper / junos 12.3-r12-s12 12.3-r12-s12.x
juniper / junos 17.3-r2-s4 17.3-r2-s4.x
juniper / junos 17.4-r2-s8 17.4-r2-s8.x
juniper / junos 12.3-r10-s1 12.3-r10-s1.x
juniper / junos 12.3-r10-s2 12.3-r10-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 18.2-r3-s2 18.2-r3-s2.x
juniper / junos 18.1-r3-s8 18.1-r3-s8.x
juniper / junos 19.2-r1-s3 19.2-r1-s3.x
juniper / junos 19.4-r1 19.4-r1.x
juniper / junos 19.3-r2 19.3-r2.x
juniper / junos 19.1-r2 19.1-r2.x
juniper / junos 18.4-r3 18.4-r3.x
juniper / junos 18.4-r2-s3 18.4-r2-s3.x
juniper / junos 18.1-r3-s9 18.1-r3-s9.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 19.2-r1-s4 19.2-r1-s4.x
juniper / junos 20.1-r1 20.1-r1.x
juniper / junos 19.4-r1-s1 19.4-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 18.2-r3-s3 18.2-r3-s3.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 15.1-r7-s7 15.1-r7-s7.x
juniper / junos 12.3-r12-s15 12.3-r12-s15.x
juniper / junos 18.2-r3-s4 18.2-r3-s4.x
juniper / junos 17.3-r2-s5 17.3-r2-s5.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 19.1-r2-s1 19.1-r2-s1.x
juniper / junos 19.1-r3 19.1-r3.x
juniper / junos 19.1-r3-s1 19.1-r3-s1.x
juniper / junos 15.1-r7-s6 15.1-r7-s6.x
juniper / junos 19.4-r1-s2 19.4-r1-s2.x
juniper / junos 20.1-r1-s1 20.1-r1-s1.x
juniper / junos 17.4-r3-s2 17.4-r3-s2.x
juniper / junos 17.4-r3-s3 17.4-r3-s3.x
juniper / junos 20.2-r1 20.2-r1.x
juniper / junos 20.1-r1-s2 20.1-r1-s2.x
juniper / junos 20.1-r1-s3 20.1-r1-s3.x
juniper / junos 19.4-r2 19.4-r2.x
juniper / junos 19.4-r2-s1 19.4-r2-s1.x
juniper / junos 19.3-r2-s3 19.3-r2-s3.x
juniper / junos 19.1-r3-s2 19.1-r3-s2.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 18.2-r3-s5 18.2-r3-s5.x
juniper / junos 18.1-r3-s10 18.1-r3-s10.x
juniper / junos 19.2-r2 19.2-r2.x
juniper / junos 17.3-r3-s8 17.3-r3-s8.x
juniper / junos 17.4-r2-s11 17.4-r2-s11.x
juniper / junos 19.3-r2-s4 19.3-r2-s4.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 19.4-r2-s2 19.4-r2-s2.x
juniper / junos 19.2-r3 19.2-r3.x
juniper / junos 18.4-r3-s5 18.4-r3-s5.x
juniper / junos 19.4-r3 19.4-r3.x
juniper / junos 19.3-r2-s5 19.3-r2-s5.x
juniper / junos 19.3-r3 19.3-r3.x
juniper / junos 19.2-r1-s5 19.2-r1-s5.x
juniper / junos 19.1-r3-s3 19.1-r3-s3.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 17.3-r3-s9 17.3-r3-s9.x
juniper / junos 17.3-r3-s10 17.3-r3-s10.x
juniper / junos 15.1-r7-s8 15.1-r7-s8.x
juniper / junos 19.1-r1-s5 19.1-r1-s5.x
juniper / junos 18.4-r1-s7 18.4-r1-s7.x
juniper / junos 12.3-r12-s16 12.3-r12-s16.x
juniper / junos 20.3-r1 20.3-r1.x
juniper / junos 18.2-r2-s7 18.2-r2-s7.x
juniper / junos 18.1-r3-s11 18.1-r3-s11.x
juniper / junos 19.2-r2-s1 19.2-r2-s1.x
juniper / junos 18.2-r3-s6 18.2-r3-s6.x
juniper / junos 18.2-r1-s2 18.2-r1-s2.x
juniper / junos 20.1-r1-s4 20.1-r1-s4.x
juniper / junos 19.1-r3-s4 19.1-r3-s4.x
juniper / junos 18.4-r3-s6 18.4-r3-s6.x
juniper / junos 18.2-r3-s7 18.2-r3-s7.x
juniper / junos 20.3-r1-s1 20.3-r1-s1.x
juniper / junos 20.2-r1-s3 20.2-r1-s3.x
juniper / junos 19.2-r3-s1 19.2-r3-s1.x
juniper / junos 18.4-r3-s7 18.4-r3-s7.x
juniper / junos 18.1-r3-s12 18.1-r3-s12.x
juniper / junos 17.4-r2-s12 17.4-r2-s12.x
juniper / junos 17.3-r3-s11 17.3-r3-s11.x
juniper / junos 19.4-r3-s1 19.4-r3-s1.x
juniper / junos 19.4-r2-s3 19.4-r2-s3.x
juniper / junos 20.2-r2 20.2-r2.x
juniper / junos 20.2-r2-s1 20.2-r2-s1.x
juniper / junos 17.4-r3-s4 17.4-r3-s4.x
juniper / junos 19.4-r1-s3 19.4-r1-s3.x
juniper / junos 19.2-r1-s6 19.2-r1-s6.x
juniper / junos 19.1-r2-s2 19.1-r2-s2.x
juniper / junos 20.4-r1 20.4-r1.x
juniper / junos 20.2-r2-s2 20.2-r2-s2.x
juniper / junos 20.1-r2 20.1-r2.x
juniper / junos 20.1-r2-s1 20.1-r2-s1.x
juniper / junos 20.4-r1-s1 20.4-r1-s1.x
juniper / junos 19.1-r1-s6 19.1-r1-s6.x
juniper / junos 20.2-r2-s3 20.2-r2-s3.x
juniper / junos 20.3-r2 20.3-r2.x
juniper / junos 19.3-r3-s1 19.3-r3-s1.x
juniper / junos 18.4-r2-s7 18.4-r2-s7.x
juniper / junos 20.2-r3 20.2-r3.x
juniper / junos 19.4-r3-s2 19.4-r3-s2.x
juniper / junos 12.3-r12-s17 12.3-r12-s17.x
juniper / junos 19.2-r3-s2 19.2-r3-s2.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.