CVE-2020-1661: On Juniper Networks Junos OS devices configured as a DHCP forwarder, the Juniper Networks Dynamic Host Configuration Protocol Daemon (jdhcp) process m...

Description

On Juniper Networks Junos OS devices configured as a DHCP forwarder, the Juniper Networks Dynamic Host Configuration Protocol Daemon (jdhcp) process might crash when receiving a malformed DHCP packet. This issue only affects devices configured as DHCP forwarder with forward-only option, that forward specified DHCP client packets, without creating a new subscriber session. The jdhcpd daemon automatically restarts without intervention, but continuous receipt of the malformed DHCP packet will repeatedly crash jdhcpd, leading to an extended Denial of Service (DoS) condition. This issue can be triggered only by DHCPv4, it cannot be triggered by DHCPv6. This issue affects Juniper Networks Junos OS: 12.3 versions prior to 12.3R12-S16; 12.3X48 versions prior to 12.3X48-D105 on SRX Series; 14.1X53 versions prior to 14.1X53-D60 on EX and QFX Series; 15.1 versions prior to 15.1R7-S7; 15.1X49 versions prior to 15.1X49-D221, 15.1X49-D230 on SRX Series; 15.1X53 versions prior to 15.1X53-D593 on EX2300/EX3400; 16.1 versions prior to 16.1R7-S5.

Metrics

CVSS 3.1

5.3/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS Probability

0.99%

57.9th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Juniper	Junos	12.3
Juniper	Junos	15.1
Juniper	Junos	16.1
Juniper	Junos	12.3x48
Juniper	Junos	15.1x49
Juniper	Junos	15.1x53
Juniper	Junos	14.1x53

References

https://kb.juniper.net/JSA11056Vendor Advisory
https://kb.juniper.net/JSA11056Vendor Advisory

Timeline

Published: Oct 16, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-1661?

On Juniper Networks Junos OS devices configured as a DHCP forwarder, the Juniper Networks Dynamic Host Configuration Protocol Daemon (jdhcp) process might crash when receiving a malformed DHCP packet. This issue only affects devices configured as DHCP forwarder with forward-only option, that forward specified DHCP client packets, without creating a new subscriber session. The jdhcpd daemon automatically restarts without intervention, but continuous receipt of the malformed DHCP packet will repeatedly crash jdhcpd, leading to an extended Denial of Service (DoS) condition. This issue can be triggered only by DHCPv4, it cannot be triggered by DHCPv6. This issue affects Juniper Networks Junos OS: 12.3 versions prior to 12.3R12-S16; 12.3X48 versions prior to 12.3X48-D105 on SRX Series; 14.1X53 versions prior to 14.1X53-D60 on EX and QFX Series; 15.1 versions prior to 15.1R7-S7; 15.1X49 versions prior to 15.1X49-D221, 15.1X49-D230 on SRX Series; 15.1X53 versions prior to 15.1X53-D593 on EX2300/EX3400; 16.1 versions prior to 16.1R7-S5.

How severe is CVE-2020-1661?

CVE-2020-1661 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 0.99% probability of exploitation in the next 30 days.

How do I fix CVE-2020-1661?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.