Vulnerability Database

394,002

Total vulnerabilities in the database

CVE-2020-1656 — juniper / junos

Improper Input Validation

The DHCPv6 Relay-Agent service, part of the Juniper Enhanced jdhcpd daemon shipped with Juniper Networks Junos OS has an Improper Input Validation vulnerability which will result in a Denial of Service (DoS) condition when a DHCPv6 client sends a specific DHPCv6 message allowing an attacker to potentially perform a Remote Code Execution (RCE) attack on the target device. Continuous receipt of the specific DHCPv6 client message will result in an extended Denial of Service (DoS) condition. If adjacent devices are also configured to relay DHCP packets, and are not affected by this issue and simply transparently forward unprocessed client DHCPv6 messages, then the attack vector can be a Network-based attack, instead of an Adjacent-device attack. No other DHCP services are affected. Receipt of the packet without configuration of the DHCPv6 Relay-Agent service, will not result in exploitability of this issue. This issue affects Juniper Networks Junos OS: 12.3 versions prior to 12.3R12-S15; 12.3X48 versions prior to 12.3X48-D95; 14.1X53 versions prior to 14.1X53-D53; 15.1 versions prior to 15.1R7-S6; 15.1X49 versions prior to 15.1X49-D200; 15.1X53 versions prior to 15.1X53-D593; 16.1 versions prior to 16.1R7-S7; 16.2 versions prior to 16.2R2-S11; 17.1 versions prior to 17.1R2-S11, 17.1R3-S2; 17.2 versions prior to 17.2R3-S3; 17.2X75 versions prior to 17.2X75-D44; 17.3 versions prior to 17.3R3-S7; 17.4 versions prior to 17.4R2-S9, 17.4R3; 18.1 versions prior to 18.1R3-S9; 18.2 versions prior to 18.2R2-S6, 18.2R3-S2; 18.2X75 versions prior to 18.2X75-D12, 18.2X75-D33, 18.2X75-D435, 18.2X75-D60; 18.3 versions prior to 18.3R1-S7, 18.3R2-S3, 18.3R3-S1; 18.4 versions prior to 18.4R1-S5, 18.4R2-S3, 18.4R3; 19.1 versions prior to 19.1R1-S4, 19.1R2; 19.2 versions prior to 19.2R1-S3, 19.2R2; 19.3 versions prior to 19.3R2.

  • Published: Oct 16, 2020
  • Updated: Oct 5, 2026
  • CVE: CVE-2020-1656
  • Severity: High
  • Exploit:
  • CISA KEV:

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
Software Affected versions
juniper / junos = 12.3
juniper / junos = 12.3-r1
juniper / junos = 12.3-r10
juniper / junos = 12.3-r10-s1
juniper / junos = 12.3-r10-s2
juniper / junos = 12.3-r11
juniper / junos = 12.3-r12
juniper / junos = 12.3-r12-s1
juniper / junos = 12.3-r12-s11
juniper / junos = 12.3-r12-s12
juniper / junos = 12.3-r12-s13
juniper / junos = 12.3-r12-s14
juniper / junos = 12.3x48
juniper / junos = 12.3x48-d10
juniper / junos = 12.3x48-d100
juniper / junos = 12.3x48-d15
juniper / junos = 12.3x48-d20
juniper / junos = 12.3x48-d25
juniper / junos = 12.3x48-d30
juniper / junos = 12.3x48-d35
juniper / junos = 12.3x48-d40
juniper / junos = 12.3x48-d45
juniper / junos = 12.3x48-d50
juniper / junos = 12.3x48-d51
juniper / junos = 12.3x48-d55
juniper / junos = 12.3x48-d60
juniper / junos = 12.3x48-d65
juniper / junos = 12.3x48-d70
juniper / junos = 12.3x48-d75
juniper / junos = 12.3x48-d80
juniper / junos = 12.3x48-d90
juniper / junos = 14.1x53
juniper / junos = 14.1x53-d10
juniper / junos = 14.1x53-d121
juniper / junos = 14.1x53-d15
juniper / junos = 14.1x53-d16
juniper / junos = 14.1x53-d25
juniper / junos = 14.1x53-d26
juniper / junos = 14.1x53-d27
juniper / junos = 14.1x53-d30
juniper / junos = 14.1x53-d34
juniper / junos = 14.1x53-d35
juniper / junos = 14.1x53-d40
juniper / junos = 14.1x53-d42
juniper / junos = 14.1x53-d43
juniper / junos = 14.1x53-d44
juniper / junos = 14.1x53-d45
juniper / junos = 14.1x53-d48
juniper / junos = 14.1x53-d50
juniper / junos = 14.1x53-d51
juniper / junos = 14.1x53-d52
juniper / junos = 15.1
juniper / junos = 15.1-a1
juniper / junos = 15.1-f
juniper / junos = 15.1-f1
juniper / junos = 15.1-f2
juniper / junos = 15.1-f2-s1
juniper / junos = 15.1-f2-s2
juniper / junos = 15.1-f2-s3
juniper / junos = 15.1-f2-s4
juniper / junos = 15.1-f3
juniper / junos = 15.1-f4
juniper / junos = 15.1-f5
juniper / junos = 15.1-f5-s7
juniper / junos = 15.1-f6
juniper / junos = 15.1-f6-s1
juniper / junos = 15.1-f6-s12
juniper / junos = 15.1-f6-s2
juniper / junos = 15.1-f6-s3
juniper / junos = 15.1-f6-s4
juniper / junos = 15.1-f6-s7
juniper / junos = 15.1-f7
juniper / junos = 15.1-r1
juniper / junos = 15.1-r2
juniper / junos = 15.1-r3
juniper / junos = 15.1-r4
juniper / junos = 15.1-r4-s7
juniper / junos = 15.1-r4-s8
juniper / junos = 15.1-r4-s9
juniper / junos = 15.1-r5
juniper / junos = 15.1-r5-s1
juniper / junos = 15.1-r5-s5
juniper / junos = 15.1-r5-s6
juniper / junos = 15.1-r6
juniper / junos = 15.1-r6-s1
juniper / junos = 15.1-r6-s2
juniper / junos = 15.1-r6-s6
juniper / junos = 15.1-r7
juniper / junos = 15.1-r7-s1
juniper / junos = 15.1-r7-s2
juniper / junos = 15.1-r7-s3
juniper / junos = 15.1-r7-s4
juniper / junos = 15.1-r7-s5
juniper / junos = 15.1x49
juniper / junos = 15.1x49-d10
juniper / junos = 15.1x49-d100
juniper / junos = 15.1x49-d110
juniper / junos = 15.1x49-d120
juniper / junos = 15.1x49-d130
juniper / junos = 15.1x49-d140
juniper / junos = 15.1x49-d15
juniper / junos = 15.1x49-d150
juniper / junos = 15.1x49-d160
juniper / junos = 15.1x49-d170
juniper / junos = 15.1x49-d180
juniper / junos = 15.1x49-d190
juniper / junos = 15.1x49-d20
juniper / junos = 15.1x49-d25
juniper / junos = 15.1x49-d30
juniper / junos = 15.1x49-d35
juniper / junos = 15.1x49-d40
juniper / junos = 15.1x49-d45
juniper / junos = 15.1x49-d50
juniper / junos = 15.1x49-d55
juniper / junos = 15.1x49-d60
juniper / junos = 15.1x49-d65
juniper / junos = 15.1x49-d70
juniper / junos = 15.1x49-d75
juniper / junos = 15.1x49-d80
juniper / junos = 15.1x49-d90
juniper / junos = 15.1x53
juniper / junos = 15.1x53-d10
juniper / junos = 15.1x53-d20
juniper / junos = 15.1x53-d21
juniper / junos = 15.1x53-d210
juniper / junos = 15.1x53-d230
juniper / junos = 15.1x53-d231
juniper / junos = 15.1x53-d232
juniper / junos = 15.1x53-d233
juniper / junos = 15.1x53-d234
juniper / junos = 15.1x53-d235
juniper / junos = 15.1x53-d236
juniper / junos = 15.1x53-d237
juniper / junos = 15.1x53-d25
juniper / junos = 15.1x53-d30
juniper / junos = 15.1x53-d31
juniper / junos = 15.1x53-d32
juniper / junos = 15.1x53-d33
juniper / junos = 15.1x53-d34
juniper / junos = 15.1x53-d40
juniper / junos = 15.1x53-d45
juniper / junos = 15.1x53-d47
juniper / junos = 15.1x53-d470
juniper / junos = 15.1x53-d48
juniper / junos = 15.1x53-d495
juniper / junos = 15.1x53-d50
juniper / junos = 15.1x53-d51
juniper / junos = 15.1x53-d52
juniper / junos = 15.1x53-d55
juniper / junos = 15.1x53-d56
juniper / junos = 15.1x53-d57
juniper / junos = 15.1x53-d58
juniper / junos = 15.1x53-d59
juniper / junos = 15.1x53-d590
juniper / junos = 15.1x53-d591
juniper / junos = 15.1x53-d592
juniper / junos = 15.1x53-d60
juniper / junos = 15.1x53-d61
juniper / junos = 15.1x53-d62
juniper / junos = 15.1x53-d63
juniper / junos = 15.1x53-d64
juniper / junos = 15.1x53-d65
juniper / junos = 15.1x53-d66
juniper / junos = 15.1x53-d67
juniper / junos = 15.1x53-d68
juniper / junos = 15.1x53-d69
juniper / junos = 15.1x53-d70
juniper / junos = 16.1
juniper / junos = 16.1-r1
juniper / junos = 16.1-r2
juniper / junos = 16.1-r3
juniper / junos = 16.1-r3-s10
juniper / junos = 16.1-r3-s11
juniper / junos = 16.1-r4
juniper / junos = 16.1-r4-s12
juniper / junos = 16.1-r4-s2
juniper / junos = 16.1-r4-s3
juniper / junos = 16.1-r4-s4
juniper / junos = 16.1-r4-s6
juniper / junos = 16.1-r5
juniper / junos = 16.1-r5-s4
juniper / junos = 16.1-r6-s1
juniper / junos = 16.1-r6-s6
juniper / junos = 16.1-r7
juniper / junos = 16.1-r7-s2
juniper / junos = 16.1-r7-s3
juniper / junos = 16.1-r7-s4
juniper / junos = 16.1-r7-s5
juniper / junos = 16.1-r7-s6
juniper / junos = 16.2
juniper / junos = 16.2-r1
juniper / junos = 16.2-r2
juniper / junos = 16.2-r2-s1
juniper / junos = 16.2-r2-s10
juniper / junos = 16.2-r2-s2
juniper / junos = 16.2-r2-s5
juniper / junos = 16.2-r2-s6
juniper / junos = 16.2-r2-s7
juniper / junos = 16.2-r2-s8
juniper / junos = 16.2-r2-s9
juniper / junos = 17.1
juniper / junos = 17.1-r1
juniper / junos = 17.1-r2
juniper / junos = 17.1-r2-s1
juniper / junos = 17.1-r2-s10
juniper / junos = 17.1-r2-s2
juniper / junos = 17.1-r2-s3
juniper / junos = 17.1-r2-s4
juniper / junos = 17.1-r2-s5
juniper / junos = 17.1-r2-s6
juniper / junos = 17.1-r2-s7
juniper / junos = 17.1-r2-s8
juniper / junos = 17.1-r2-s9
juniper / junos = 17.1-r3-s1
juniper / junos = 17.2
juniper / junos = 17.2-r1
juniper / junos = 17.2-r1-s1
juniper / junos = 17.2-r1-s2
juniper / junos = 17.2-r1-s3
juniper / junos = 17.2-r1-s4
juniper / junos = 17.2-r1-s5
juniper / junos = 17.2-r1-s7
juniper / junos = 17.2-r1-s8
juniper / junos = 17.2-r2
juniper / junos = 17.2-r2-s11
juniper / junos = 17.2-r2-s6
juniper / junos = 17.2-r2-s7
juniper / junos = 17.2-r3-s1
juniper / junos = 17.2-r3-s2
juniper / junos = 17.2x75
juniper / junos = 17.3
juniper / junos = 17.3-r1-s1
juniper / junos = 17.3-r2
juniper / junos = 17.3-r2-s1
juniper / junos = 17.3-r2-s2
juniper / junos = 17.3-r2-s3
juniper / junos = 17.3-r2-s4
juniper / junos = 17.3-r2-s5
juniper / junos = 17.3-r3
juniper / junos = 17.3-r3-s1
juniper / junos = 17.3-r3-s2
juniper / junos = 17.3-r3-s3
juniper / junos = 17.3-r3-s4
juniper / junos = 17.3-r3-s5
juniper / junos = 17.3-r3-s6
juniper / junos = 17.4
juniper / junos = 17.4-r1
juniper / junos = 17.4-r1-s1
juniper / junos = 17.4-r1-s2
juniper / junos = 17.4-r1-s4
juniper / junos = 17.4-r1-s5
juniper / junos = 17.4-r1-s6
juniper / junos = 17.4-r1-s7
juniper / junos = 17.4-r2
juniper / junos = 17.4-r2-s1
juniper / junos = 17.4-r2-s2
juniper / junos = 17.4-r2-s3
juniper / junos = 17.4-r2-s4
juniper / junos = 17.4-r2-s5
juniper / junos = 17.4-r2-s6
juniper / junos = 17.4-r2-s7
juniper / junos = 17.4-r2-s8
juniper / junos = 18.1
juniper / junos = 18.1-r1
juniper / junos = 18.1-r2
juniper / junos = 18.1-r2-s1
juniper / junos = 18.1-r2-s2
juniper / junos = 18.1-r2-s4
juniper / junos = 18.1-r3
juniper / junos = 18.1-r3-s1
juniper / junos = 18.1-r3-s2
juniper / junos = 18.1-r3-s3
juniper / junos = 18.1-r3-s4
juniper / junos = 18.1-r3-s6
juniper / junos = 18.1-r3-s7
juniper / junos = 18.1-r3-s8
juniper / junos = 18.2
juniper / junos = 18.2-r1
juniper / junos = 18.2-r1-s3
juniper / junos = 18.2-r1-s4
juniper / junos = 18.2-r1-s5
juniper / junos = 18.2-r2
juniper / junos = 18.2-r2-s1
juniper / junos = 18.2-r2-s2
juniper / junos = 18.2-r2-s3
juniper / junos = 18.2-r2-s4
juniper / junos = 18.2-r2-s5
juniper / junos = 18.2-r3
juniper / junos = 18.2-r3-s1
juniper / junos = 18.2x75
juniper / junos = 18.2x75-d20
juniper / junos = 18.2x75-d30
juniper / junos = 18.2x75-d40
juniper / junos = 18.2x75-d411
juniper / junos = 18.2x75-d51
juniper / junos = 18.3
juniper / junos = 18.3-r1
juniper / junos = 18.3-r1-s1
juniper / junos = 18.3-r1-s2
juniper / junos = 18.3-r1-s3
juniper / junos = 18.3-r1-s5
juniper / junos = 18.3-r1-s6
juniper / junos = 18.3-r2
juniper / junos = 18.3-r2-s1
juniper / junos = 18.3-r2-s2
juniper / junos = 18.3-r3
juniper / junos = 18.4
juniper / junos = 18.4-r1
juniper / junos = 18.4-r1-s1
juniper / junos = 18.4-r1-s2
juniper / junos = 18.4-r2
juniper / junos = 18.4-r2-s1
juniper / junos = 18.4-r2-s2
juniper / junos = 19.1
juniper / junos = 19.1-r1
juniper / junos = 19.1-r1-s1
juniper / junos = 19.1-r1-s2
juniper / junos = 19.1-r1-s3
juniper / junos = 19.2
juniper / junos = 19.2-r1
juniper / junos = 19.2-r1-s1
juniper / junos = 19.2-r1-s2
juniper / junos = 19.3
juniper / junos = 19.3-r1
juniper / junos = 19.3-r1-s1

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.