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2013-07 Security Bulletin: Junos: Kernel crash during processing of certain ARP requests when proxy-arp and arp-resp options enabled (CVE-2013-4686)

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Categories:
Security Advisories ID: JSA10576
Last Updated: 10 Jul 2013
Version: 2.0

Product Affected:
This issue can affect any product or platform running Junos OS 10.4, 11.4, 11.4X27, 12.1X44, 12.1, 12.2, or 12.3

Problem:
The Junos kernel may crash when receiving a certain ARP request from a client when a 'family inet' interface:
  • is configured as a VLAN interface with an unnumbered address based on lo0
  • lo0 is configured with a non-/32 address, and
  • both 'proxy-arp unrestricted' and 'arp-resp unrestricted' are enabled

An example affected configuration is shown below:
interfaces {
    ge-3/0/0 {
        interface-transmit-statistics;
        flexible-vlan-tagging;
        encapsulation flexible-ethernet-services;
        unit 4000 {
            arp-resp unrestricted;
            proxy-arp unrestricted;
            vlan-tags outer 1 inner 4000;
            family inet {
                mac-validate strict;
                unnumbered-address lo0.0;
            }
        }
    }
    lo0 {
        unit 0 {
            family inet {
                address 10.0.0.1/24;
            }
        }
    }
    ge-3/1/0 {
        unit 0 {
            family inet {
                address 20.0.0.2/24;
                address 10.0.0.4/31;
            }
        }
    }
}
routing-options {
    static {
        route 11.0.0.0/24 next-hop 20.0.0.1;
    }
}
This issue was found during internal product security testing.

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-2013-4686.

Solution:
All Junos OS software releases built on or after 2013-06-09 have fixed this specific issue. Releases containing the fix specifically include: 10.4R14, 11.4R8, 11.4X27.43 (BBE), and 12.1X44-D20 (SRX), 12.1R6, 12.2R4, 12.3R2, 13.1R1, and all subsequent releases (i.e. all releases built after 13.1R1).

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 842091 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:
If the 'arp-resp unrestricted' and/or 'proxy-arp unrestricted' options are not required, removing either configuration statement will completely mitigate this kernel crash. Additionally, if there is no specific need to use a non-/32 address on the lo0 interface, changing the mask to /32 will also mitigate this issue.

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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