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2020-04 Security Bulletin: Junos OS: MX Series: Crafted packets traversing a Broadband Network Gateway (BNG) configured with IPv6 NDP proxy could lead to Denial of Service (CVE-2020-1633)

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Article ID: JSA11012 SECURITY_ADVISORIES Last Updated: 08 Apr 2020Version: 1.0
Product Affected:
This issue affects Junos OS 17.4, 18.1, 18.2, 18.2X75, 18.3, 18.4, 19.1, 19.2. Affected platforms: MX Series.
Problem:

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.


The proxy ARP/NDP feature is enabled by default for EVPNs. A sample EVPN configuration is shown below:

[routing-instances <name> protocols evpn]


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


This issue was seen during production usage.


This issue has been assigned CVE-2020-1633.
 

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.

This issue is being tracked as 1451959.
 

Workaround:

Configure 'no-arp-suppression' to disable Proxy ARP/NDP feature. For example:

[routing-instances <name> protocols evpn]
# set no-arp-suppression
 
Implementation:
How to obtain fixed software:

Security vulnerabilities in Junos are fixed in the next available Maintenance Release of each supported Junos version. In some cases, a Maintenance Release is not planned to be available in an appropriate time-frame. For these cases, Service Releases are made available in order to be more timely. Security Advisory and Security Notices will indicate which Maintenance and Service  Releases contain fixes for the issues described. Upon request to JTAC, customers will be provided download instructions for a Service Release. Although Juniper does not provide formal Release Note documentation for a Service Release, a list of "PRs fixed" can be provided on request.
 
Modification History:
‚Äč2020-04-08: Initial publication
CVSS Score:
7.4 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H)
Severity Level:
High
Severity Assessment:
Information for how Juniper Networks uses CVSS can be found at KB 16446 "Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."

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