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2014-01 Security Bulletin: Junos: rpd crash when attempting to send an oversized BGP UPDATE (CVE-2014-0616)

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Categories:
Security Advisories ID: JSA10609
Last Updated: 08 Jan 2014
Version: 1.0

Product Affected:
This issue can affect any product or platform running Junos OS.

Problem:
Under specific time-sensitive circumstances, if BGP determines that an UPDATE is too big to be sent to a peer, and immediately attempts to send a withdraw message, the routing daemon (rpd) may crash. An example of an oversized BGP UPDATE is one where a very long AS_PATH would cause the packet to exceed the maximum BGP message size (4096 bytes). The use of a very large number of BGP Communities can also be used to exceed the maximum BGP message size.

This issue can be triggered in both IPv4 and IPv6 environments.

The following message would be seen in the syslog just prior to the rpd core:
"path attribute too big. Cannot build update."
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-2014-0616.

Solution:
The following software releases have been updated to resolve this specific issue:
  • All Junos OS software releases built on or after 2013-12-20, or
  • Junos OS 10.4R16, 11.4R10, 12.1R8-S3, 12.1X44-D30, 12.1X45-D20, 12.1X46-D10, 12.2R7, 12.3R4-S2, 12.3R5, 13.1R3-S1, 13.2R2, 13.3R1, and all subsequent releases (i.e. all releases built after 13.3R1).

Customers can confirm the build date of any Junos OS release by issuing the command 'show version detail'.

This issue is being tracked as PR 918734 and is visible on the Customer Support website.


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:
One way to limit AS_PATH length is to create an import policy with an associated as-path filter that will drop updates with AS_PATH longer than a specified number of ASes (eg. 40). The AS_PATH filter can be any length. In the following example, AS_PATHs with more than 40 ASes, which would take 80 bytes with 2-byte AS and 160 bytes with 4-byte AS, are rejected:
policy-statement LIMIT-AS_PATH {
  term 10 {
    from {
      protocol bgp;
      as-path MAX-AS_PATH;
    }
    then reject;
  }
}

as-path MAX-AS_PATH ".{41,}"

The community-count policy match statement can be used to restrict the number of communities received:
policy-statement LIMIT-COMMUNITIES {
  term 20 {
    from {
      protocol bgp;
      community-count 50 orhigher;
    }
    then reject;
  }
}
Note that the 'community-count' match statement is available in Junos OS 10.4 and later releases.

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.

Related Links:

CVSS Score:
7.1 (AV:N/AC:M/Au:N/C:N/I:N/A:C)

Risk Level:
High

Risk 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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