CVE-2020-1633

IPv6 traffic loss via stale MAC entries

Published Apr 9, 2020 · Updated Sep 17, 2024

Improper input validation in Juniper Networks Junos OS on MX Series allows adjacent attackers to interrupt legitimate IPv6 traffic. The IPv6 NDP proxy on an EVPN leaf node accepts a crafted NDPv6 packet relayed through a BNG and leaves a stale MAC address entry. The affected configuration requires IPv6, an MX Series BNG, and the EVPN NDP proxy; the stale entry causes legitimate traffic to be discarded.

CVSS severity7.4
High
EPSS probability0.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Improper input validation in Juniper Networks Junos OS on MX Series allows adjacent attackers to interrupt legitimate IPv6 traffic. The IPv6 NDP proxy on an EVPN leaf node accepts a crafted NDPv6 packet relayed through a BNG and leaves a stale MAC address entry. The affected configuration requires IPv6, an MX Series BNG, and the EVPN NDP proxy; the stale entry causes legitimate traffic to be discarded.

The record

CVE
CVE-2020-1633
Published
Apr 9, 2020
Updated
Sep 17, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-20, T1499.004
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 9, 2020CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=17.4 <17.4R2-S9, 17.4R3
  2. Affected versionversion=18.1 <18.1R3-S9
  3. Affected versionversion=18.2 <18.2R2-S7, 18.2R3-S3
  4. Affected versionversion=18.2X75 <18.2X75-D33, 18.2X75-D411, 18.2X75-D420, 18.2X75-D60
  5. Affected versionversion=18.3 <18.3R1-S7, 18.3R2-S3, 18.3R3
  6. Affected versionversion=18.4 <18.4R1-S5, 18.4R2-S2, 18.4R3
  7. Affected versionversion=19.1 <19.1R1-S4, 19.1R2
  8. Affected versionversion=19.2 <19.2R1-S3, 19.2R2

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=17.4 <17.4R2-S9, 17.4R3; version=18.1 <18.1R3-S9; version=18.2 <18.2R2-S7, 18.2R3-S3; version=18.2X75 <18.2X75-D33, 18.2X75-D411, 18.2X75-D420, 18.2X75-D60; version=18.3 <18.3R1-S7, 18.3R2-S3, 18.3R3; version=18.4 <18.4R1-S5, 18.4R2-S2, 18.4R3; version=19.1 <19.1R1-S4, 19.1R2; version=19.2 <19.2R1-S3, 19.2R2

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.3NIST NVDAV:A/AC:L/Au:N/C:N/I:N/A:P
7.4Juniper NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo