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             AUSCERT External Security Bulletin Redistribution

         2016-01 Security Bulletin: Junos: EX4300 Series denial of
            service due to artificial loop in network topology
                              14 January 2016


        AusCERT Security Bulletin Summary

Product:           Juniper EX4300 Series
Publisher:         Juniper Networks
Operating System:  Network Appliance
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2016-1260  

Original Bulletin: 

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2016-01 Security Bulletin: Junos: EX4300 Series denial of service due to 
artificial loop in network topology (CVE-2016-1260)



EX Series


SIRT Advisory

Security Advisories ID: JSA10719

Last Updated: 12 Jan 2016

Version: 1.0

Product Affected:

This issue can affect EX4300-Series switches.


A certain type of legitimate traffic which can be maliciously crafted or may 
be valid traffic for networking requirements in customer sites received from 
ingress interfaces through the EX-PFE leak out blocked Spanning Tree Protocol
egress interfaces creating an artificial loop in network topology. This can 
lead to a high bandwidth usage denial of service condition. Continued packets
can create a persistent denial of service condition.

This issue is most likely to occur in Virtual Chassis (VC) configurations.

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

No other Juniper Networks products or platforms are affected by this issue.

This issue has been assigned CVE-2016-1260.


The following software releases have been updated to resolve this specific 
issue: Junos OS 13.2X51-D36, 13.2X51-D39, 14.1X53-D25, 14.1X53-D26, 15.2R1 and
all subsequent releases.

This issue is being tracked as PR 1069179 and is visible on the Customer 
Support website.


Eliminating Spanning Tree Protocol usage from the network and blocking any 
ingress or egress STP traffic may mitigate this issue.


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:

2016-01-13: Initial publication

Related Links:

KB16613: Overview of the Juniper Networks SIRT Quarterly Security Bulletin 
Publication Process

KB16765: In which releases are vulnerabilities fixed?

KB16446: Common Vulnerability Scoring System (CVSS) and Juniper's Security 

Report a Security Vulnerability - How to Contact the Juniper Networks Security
Incident Response Team

EX4300 Series denial of service due to artificial loop in network topology

CVSS Score:

5.3 (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L)

Risk Level:


Risk Assessment:

A network based attacker can create high network bandwidth usage denial of 
service condition.

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