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2020-10 Security Bulletin: Junos OS: When a DHCPv6 Relay-Agent is configured upon receipt of a specific DHCPv6 client message, Remote Code Execution may occur. (CVE-2020-1656)



Article ID: JSA11049 SECURITY_ADVISORIES Last Updated: 29 Oct 2020Version: 2.0
Product Affected:
This issue affects Junos OS 12.3, 12.3X48, 14.1X53, 15.1, 15.1X49, 15.1X53, 16.1, 16.2, 17.1, 17.2, 17.2X75, 17.3, 17.4, 18.1, 18.2, 18.2X75, 18.3, 18.4, 19.1, 19.2, 19.3.

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.

The following minimal configuration is required:

[forwarding-options dhcp-relay dhcpv6]

More details on DHCPV6 Relay-Agent configuration and use are located in the reference URLs.

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-2020-1656.


The following software releases have been updated to resolve this specific issue: Junos OS 12.3R12-S15, 12.3X48-D100, 12.3X48-D95, 14.1X53-D53, 15.1R7-S6, 15.1X49-D200, 15.1X53-D593, 16.1R7-S7, 16.2R2-S11, 17.1R2-S11, 17.1R3-S2, 17.2R3-S3, 17.2X75-D44, 17.3R3-S7, 17.4R2-S9, 17.4R3, 18.1R3-S9, 18.2R2-S6, 18.2R3-S2, 18.2X75-D12, 18.2X75-D33, 18.2X75-D435, 18.2X75-D60, 18.3R1-S7, 18.3R2-S3, 18.3R3-S1, 18.4R1-S5, 18.4R2-S3, 18.4R3, 19.1R1-S4, 19.1R2, 19.1R3, 19.2R1-S3, 19.2R2, 19.4R1, and all subsequent releases.

This issue is being tracked as 1461448.


There are no available workarounds for this issue.

Software releases or updates are available for download at
Modification History:
2020-10-14: Initial Publication.
CVSS Score:
8.8 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)
Severity Level:
Severity Assessment:
Information for how Juniper Networks uses CVSS can be found at KB 16446 "Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."

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