Junos OS: When a DHCPv6 Relay-Agent is configured upon receipt of a specific DHCPv6 client message, Remote Code Execution may occur.

Description

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.

Timeline

Scores

EPSS (exploitation in 30 days)

1.1% · top 34% of all CVEs (7 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.8.

Weakness

• Denial of Service (DoS)
• Remote Code Execution
• CWE-476 NULL Pointer Dereference (opens in a new tab)All about CWE-476 and its CVEs
• CWE-20 Improper Input Validation (opens in a new tab)All about CWE-20 and its CVEs

Affected products

• Juniper Networks · Junos OS

  • affected 12.3 – < 12.3R12-S15
  • affected 12.3X48 – < 12.3X48-D95
  • affected 14.1X53 – < 14.1X53-D53
  • affected 15.1 – < 15.1R7-S6
  • affected 15.1X49 – < 15.1X49-D200
  • affected 15.1X53 – < 15.1X53-D593
  • affected 16.1 – < 16.1R7-S7
  • affected 16.2 – < 16.2R2-S11
  • affected 17.1 – < 17.1R2-S11, 17.1R3-S2
  • affected 17.2 – < 17.2R3-S3
  • affected 17.2X75 – < 17.2X75-D44
  • affected 17.3 – < 17.3R3-S7
  • affected 17.4 – < 17.4R2-S9, 17.4R3
  • affected 18.1 – < 18.1R3-S9
  • affected 18.2 – < 18.2R2-S6, 18.2R3-S2
  • affected 18.2X75 – < 18.2X75-D12, 18.2X75-D33, 18.2X75-D435, 18.2X75-D60
  • affected 18.3 – < 18.3R1-S7, 18.3R2-S3, 18.3R3-S1
  • affected 18.4 – < 18.4R1-S5, 18.4R2-S3, 18.4R3
  • affected 19.1 – < 19.1R1-S4, 19.1R2
  • affected 19.2 – < 19.2R1-S3, 19.2R2
  • affected 19.3 – < 19.3R2

What to do

Solution: 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.

Workaround: There are no available workarounds for this issue.

Exploitation: Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

References (4)

• https://kb.juniper.net/JSA11049 (opens in a new tab)x_refsource_CONFIRMx_transferred
• https://www.juniper.net/documentation/en_US/junos/topics/topic-map/dhcpv6-relay-agent-overview.html (opens in a new tab)x_refsource_MISCx_transferred
• https://www.juniper.net/documentation/en_US/junos/topics/topic-map/dhcp-relay-agent-security-devices.html (opens in a new tab)x_refsource_MISCx_transferred
• https://www.juniper.net/documentation/en_US/junos/topics/reference/command-summary/show-dhcpv6-relay-statistics.html (opens in a new tab)x_refsource_MISCx_transferred

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2020-1656](https://trackcve.app/badge/CVE-2020-1656.svg)](https://trackcve.app/cve/CVE-2020-1656)

Record last updated 17 Sept 2024, 04:14 UTC.