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CVE-2020-1633

Junos OS: MX Series: Crafted packets traversing a Broadband Network Gateway (BNG) configured with IPv6 NDP proxy could lead to Denial of Service

High7.4EPSS 0.53%
Published
Updated
Reserved
Assigned by
juniper

Description

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.

Scores

CVSS scores of CVE-2020-1633, by who scored it
Scored byCVSSScoreVector
juniperCNA (assigner)3.1High7.4CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
NVDNVD · Modified3.1Medium6.5CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS (exploitation in 30 days)
0.53% · top 55% of all CVEs (6 Nov 2026)
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.4.

Weakness

Affected products

  • Juniper Networks · Junos OS

    • affected 17.4 – < 17.4R2-S9, 17.4R3
    • affected 18.1 – < 18.1R3-S9
    • affected 18.2 – < 18.2R2-S7, 18.2R3-S3
    • affected 18.2X75 – < 18.2X75-D33, 18.2X75-D411, 18.2X75-D420, 18.2X75-D60
    • affected 18.3 – < 18.3R1-S7, 18.3R2-S3, 18.3R3
    • affected 18.4 – < 18.4R1-S5, 18.4R2-S2, 18.4R3
    • affected 19.1 – < 19.1R1-S4, 19.1R2
    • affected 19.2 – < 19.2R1-S3, 19.2R2

What to do

Solution: The following software releases have been updated to resolve this specific issue: 17.4R2-S9, 17.4R3, 18.1R3-S9, 18.2R2-S7, 18.2R3-S3, 18.2X75-D33, 18.2X75-D411, 18.2X75-D420, 18.2X75-D60, 18.3R1-S7, 18.3R2-S3, 18.3R3, 18.3R3-S1, 18.4R1-S5, 18.4R2-S2, 18.4R3, 19.1R1-S4, 19.1R2, 19.2R1-S3, 19.2R2, 19.3R1, 19.4R1, and all subsequent releases.

Workaround: Configure 'no-arp-suppression' to disable Proxy ARP/NDP feature. For example: [routing-instances <name> protocols evpn] # set no-arp-suppression

Exploitation: Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

References (1)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .