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2020-04 Security Bulletin: Junos OS: EX4300: Traffic from the network internal to the device (128.0.0.0) may be forwarded to egress interfaces (CVE-2020-1628)

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Article ID: JSA11008 SECURITY_ADVISORIES Last Updated: 08 Apr 2020Version: 1.0
Product Affected:
This issue affects Junos OS 14.1X53, 15.1, 15.1X49, 16.1, 17.1, 17.2, 17.3, 17.4, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2, 19.3. Affected platforms: EX4300.
Problem:

Juniper Networks Junos OS uses the 128.0.0.0/2 subnet for internal communications between the RE and PFEs. It was discovered that packets utilizing these IP addresses may egress an EX4300 switch, leaking configuration information such as heartbeats, kernel versions, etc. out to the Internet, leading to an information exposure vulnerability.
 

This issue affects Juniper Networks Junos OS:

  • 14.1X53 versions prior to 14.1X53-D53 on EX4300;
  • 15.1 versions prior to 15.1R7-S6 on EX4300;
  • 15.1X49 versions prior to 15.1X49-D200, 15.1X49-D210 on EX4300;
  • 16.1 versions prior to 16.1R7-S7 on EX4300;
  • 17.1 versions prior to 17.1R2-S11, 17.1R3-S2 on EX4300;
  • 17.2 versions prior to 17.2R3-S3 on EX4300;
  • 17.3 versions prior to 17.3R2-S5, 17.3R3-S7 on EX4300;
  • 17.4 versions prior to 17.4R2-S9, 17.4R3 on EX4300;
  • 18.1 versions prior to 18.1R3-S8 on EX4300;
  • 18.2 versions prior to 18.2R3-S2 on EX4300;
  • 18.3 versions prior to 18.3R2-S3, 18.3R3, 18.3R3-S1 on EX4300;
  • 18.4 versions prior to 18.4R1-S5, 18.4R2-S3, 18.4R3 on EX4300;
  • 19.1 versions prior to 19.1R1-S4, 19.1R2 on EX4300;
  • 19.2 versions prior to 19.2R1-S4, 19.2R2 on EX4300;
  • 19.3 versions prior to 19.3R1-S1, 19.3R2 on EX4300.


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-2020-1628.
 

Solution:

The following software releases have been updated to resolve this specific issue: 14.1X53-D53, 15.1R7-S6, 15.1X49-D200, 15.1X49-D210, 16.1R7-S7, 17.1R2-S11, 17.1R3-S2, 17.2R3-S3, 17.3R2-S5, 17.3R3-S7, 17.4R2-S9, 17.4R3, 18.1R3-S8, 18.2R3-S2, 18.3R2-S3, 18.3R3, 18.3R3-S1, 18.4R1-S5, 18.4R2-S3, 18.4R3, 19.1R1-S4, 19.1R2, 19.2R1-S4, 19.2R2, 19.3R1-S1, 19.3R2, 19.4R1, and all subsequent releases.

This issue is being tracked as 1426741.
 

Workaround:

Configure a firewall filter to discard packets sourced from the internal network.


Disabling the net.transit_re sysctl flag will also cause management traffic forwarded to the PFE ports to be dropped:

% sysctl -w net.transit_re=0


Note that sysctl flags do not survive a reboot.
 

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:
5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N)
Severity Level:
Medium
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."
Acknowledgements:
The Juniper SIRT would like to would like to acknowledge and thank the Telindus Service Management Center.
 

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