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2019-07 Security Bulletin: EX4300 Series: When a firewall filter is applied to a loopback interface, other firewall filters for multicast traffic may fail (CVE-2019-0048)

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Product Affected:
This issue affects the EX4300 Series running Junos OS.

On EX4300 Series switches with TCAM optimization enabled, incoming multicast traffic matches an implicit loopback filter rule first, since it has high priority. This rule is meant for reserved multicast addresses 224.0.0.x, but incorrectly matches on 224.x.x.x. Due to this bug, when a firewall filter is applied on the loopback interface, other firewall filters might stop working for multicast traffic.

The command 'show firewall filter' can be used to confirm whether the filter is working.

This issue only affects the EX4300 switch. No other products or platforms are affected by this vulnerability.

This issue affects Juniper Networks Junos OS:

  • 14.1X53 versions prior to 14.1X53-D51, 14.1X53-D115 on EX4300 Series;
  • 17.1 versions prior to 17.1R3 on EX4300 Series;
  • 17.2 versions prior to 17.2R3-S2 on EX4300 Series;
  • 17.3 versions prior to 17.3R3-S3 on EX4300 Series;
  • 17.4 versions prior to 17.4R2-S5, 17.4R3 on EX4300 Series;
  • 18.1 versions prior to 18.1R3-S1 on EX4300 Series;
  • 18.2 versions prior to 18.2R2 on EX4300 Series;
  • 18.3 versions prior to 18.3R2 on EX4300 Series.

This issue only affects EX Series switches with TCAM optimization enabled:

set system packet-forwarding-options tcam-group-optimization

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-2019-0048.


The following software releases have been updated to resolve this specific issue: 14.1X53-D51, 14.1X53-D115, 17.1R3, 17.2R3-S2, 17.3R3-S3, 17.4R2-S5, 17.4R3, 18.1R3-S1, 18.2R2, 18.3R2, 18.4R1, and all subsequent releases.

This issue is being tracked as PR 1392082 which is visible on the Customer Support website.

Note: Juniper SIRT's policy is not to evaluate releases which are beyond End of Engineering (EOE) or End of Life (EOL).

Disabling TCAM optimization will mitigate this issue.
Software Releases, patches and updates are available at
Modification History:
  • ‚Äč2019-07-10: Initial Publication
Related Links:
CVSS Score:
5.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N)
Severity Level:
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."