CVE-2020-1670

What it is

On Juniper Networks EX4300 Series, receipt of a stream of specific IPv4 packets can cause Routing Engine (RE) high CPU load, which could lead to network protocol operation issue and traffic interruption. This specific packets can originate only from within the broadcast domain where the device is connected. This issue occurs when the packets enter to the IRB interface. Only IPv4 packets can trigger this issue. IPv6 packets cannot trigger this issue. This issue affects Juniper Networks Junos OS on EX4300 series: 17.3 versions prior to 17.3R3-S9; 17.4 versions prior to 17.4R2-S11, 17.4R3-S2; 18.1 versions prior to 18.1R3-S10; 18.2 versions prior to 18.2R3-S4; 18.3 versions prior to 18.3R2-S4, 18.3R3-S2; 18.4 versions prior to 18.4R2-S4, 18.4R3-S2; 19.1 versions prior to 19.1R2-S2, 19.1R3-S1; 19.2 versions prior to 19.2R1-S5, 19.2R2-S1, 19.2R3; 19.3 versions prior to 19.3R2-S4, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2; 20.1 versions prior to 20.1R1-S3, 20.1R2.

At a glance

Exploitability

Can be exploited from the same network segment without logging in. High risk of service disruption.

Exploit odds

0.5% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2020-10-16 21:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:02 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.5% in the next 30 days (EPSS).
• Severity: 6.5 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2020-10-16 21:15 UTC

Last modified

2026-06-17 03:02 UTC

Exploit probability

0.5% · EPSS, next 30 days

Weakness

CWE-400 · Uncontrolled resource consumption

Record status

Modified

Affected

• Juniper Junos 17.3
• Juniper Junos 17.4
• Juniper Junos 18.1
• Juniper Junos 18.2
• Juniper Junos 18.3
• Juniper Junos 18.4
• Juniper Junos 19.1
• Juniper Junos 19.2

Attack profile CVSS 3.1 · 6.5

Attack vector

Adjacent network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

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