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Exception packets with specific TOS values set can cause BGP sessions to flap

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Article ID: JSA10456 SECURITY_ADVISORIES Last Updated: 09 May 2013Version: 1.0
Legacy Advisory Id:
PSN-2010-10-967
Product Affected:
This is a zero day issue which affects all software-based forwarding platforms, such as the SRX Branch Series (SRX 100, SRX 210, SRX 220, SRX 240 and SRX 650) and J Series routers. Enabling BGP is not required for this issue to be present, although BGP is one of the more likely candidates to be affected by this vulnerability.
Problem:

Exception packets (i.e. packets that needs to be sent to the RE for processing) coming into the router with TOS set to a value that implies network control traffic can cause PFE rate limiting to affect legitimate control traffic, such as BGP keepalives.

This issue only affects software-based platforms, such as the SRX Branch Series (SRX 100, SRX 210, SRX 220, SRX 240 and SRX 650) and J Series routers.
Solution:

Junos software has been enhanced to add additional checks to insure that errored packets with TOS bits are not promoted to the high priority queue. Also now insure that keepalive packets are not rate limited within the PFE.

All Junos software releases built on or after 2010-07-23 have fixed this specific issue. Releases containing the fix specifically include: 8.5S11, 9.3S13, 10.0S5.2, 10.0R4, 10.1S2.1, 10.1R2, 10.2R1 and all subsequent releases (i.e. all releases built after 10.2R1).

This issue is being tracked as PR 511206. While this PR is not viewable by customers, it can be used as a reference when discussing the issue with JTAC.

KB16765: "In which releases are vulnerabilities fixed?" describes which release vulnerabilities are fixed as per our End of Engineering and End of Life support policies.

Workaround:

Apply stricter, more precise control plane filtering on the loopback interface, limiting access to only valid IP addresses.
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.
CVSS Score:
7.8 (AV:N/AC:L/Au:N/C:N/I:N/A:C)
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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