What is CVE-2020-1633?

CVE-2020-1633 is a high-severity vulnerability in Juniper Junos, classified under Improper Input Validation. CVSS score: 7.4/10. Published 2020-04-09.

How severe is CVE-2020-1633?

High severity. CVSS v3 base score is 7.4 out of 10.

Improper input validation in Juniper Junos

CVE-2020-1633

Due to a new NDP proxy feature for EVPN leaf nodes introduced in Junos OS 17.4, crafted NDPv6 packets could transit a Junos device configured as a Broadband Network Gateway (BNG) and reach the EVPN leaf node, causing a stale MAC address entry. This could cause legitimate traffic to be discarded, leading to a Denial of Service (DoS) condition. This issue only affects Junos OS 17.4 and later releases. Prior releases do not support this feature and are unaffected by this vulnerability. This issue only affects IPv6. IPv4 ARP proxy is unaffected by this vulnerability. This issue affects Juniper Networks Junos OS: 17.4 versions prior to 17.4R2-S9, 17.4R3 on MX Series; 18.1 versions prior to 18.1R3-S9 on MX Series; 18.2 versions prior to 18.2R2-S7, 18.2R3-S3 on MX Series; 18.2X75 versions prior to 18.2X75-D33, 18.2X75-D411, 18.2X75-D420, 18.2X75-D60 on MX Series; 18.3 versions prior to 18.3R1-S7, 18.3R2-S3, 18.3R3 on MX Series; 18.4 versions prior to 18.4R1-S5, 18.4R2-S2, 18.4R3 on MX Series; 19.1 versions prior to 19.1R1-S4, 19.1R2 on MX Series; 19.2 versions prior to 19.2R1-S3, 19.2R2 on MX Series.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published 2020-04-09 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.005 (42.8th percentile), scored 2026-10-02.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 43rd percentile — 42.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000

Affected products

Juniper Junos — versions 17.4, 18.1, 18.2
Juniper Mx10
Juniper Mx10000
Juniper Mx10003
Juniper Mx104
Juniper Mx150
Juniper Mx2008
Juniper Mx2010
Juniper Mx2020
Juniper Mx204

Weakness classification (CWE)

CWE-20 — Improper Input Validation

References

kb.juniper.net/JSA11012 (Vendor Advisory)

Frequently asked questions

What is CVE-2020-1633?: CVE-2020-1633 is a high-severity vulnerability in Juniper Junos, classified under Improper Input Validation. CVSS score: 7.4/10. Published 2020-04-09.
How severe is CVE-2020-1633?: High severity. CVSS v3 base score is 7.4 out of 10.