ESB-2018.1357 - [Appliance] F5 BIG-IP products: Denial of service - Remote/unauthenticated 2018-05-03

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===========================================================================
             AUSCERT External Security Bulletin Redistribution

                               ESB-2018.1357
                             TMM vulnerability
                                3 May 2018

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           F5 BIG-IP products
Publisher:         F5 Networks
Operating System:  Network Appliance
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2018-5517  

Original Bulletin: 
   https://support.f5.com/csp/article/K25573437

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K25573437: TMM vulnerability CVE-2018-5517

Security Advisory

Original Publication Date: May 01, 2018

Security Advisory Description

Malformed TCP packets sent to a self IP address or a FastL4 virtual server may
cause an interruption of service. The control plane is not exposed to this
issue. This issue impacts the data plane virtual servers and self IPs. (
CVE-2018-5517)

Impact

This vulnerability allows remote disruption of service.

Security Advisory Status

F5 Product Development has assigned ID 702232 to this vulnerability.

To determine if your product and version have been evaluated for this
vulnerability, refer to the Applies to (see versions) box. To determine if your
release is known to be vulnerable, the components or features that are affected
by the vulnerability, and for information about releases or hotfixes that
address the vulnerability, refer to the following table.

+---------------+------+----------+----------+----------+------+--------------+
|               |      |Versions  |Fixes     |          |CVSSv3|Vulnerable    |
|Product        |Branch|known to  |introduced|Severity  |score^|component or  |
|               |      |be        |in        |          |1     |feature       |
|               |      |vulnerable|          |          |      |              |
+---------------+------+----------+----------+----------+------+--------------+
|BIG-IP (LTM,   |13.x  |13.1.0    |13.1.0.6  |          |      |TMM when      |
|AAM, AFM,      |      |          |          |          |      |processing    |
|Analytics, APM,+------+----------+----------+          |      |connections   |
|ASM, DNS, Edge |      |          |Not       |          |      |for a self IP |
|Gateway,       |12.x  |None      |Applicable|High      |7.5   |address, or a |
|GTM, Link      |      |          |          |          |      |virtual server|
|Controller,    +------+----------+----------+          |      |configured    |
|PEM,           |      |          |Not       |          |      |with a FastL4 |
|WebAccelerator,|11.x  |None      |Applicable|          |      |profile.      |
|WebSafe)       |      |          |          |          |      |              |
+---------------+------+----------+----------+----------+------+--------------+
|ARX            |6.x   |None      |Not       |Not       |None  |None          |
|               |      |          |applicable|vulnerable|      |              |
+---------------+------+----------+----------+----------+------+--------------+
|Enterprise     |3.x   |None      |Not       |Not       |None  |None          |
|Manager        |      |          |applicable|vulnerable|      |              |
+---------------+------+----------+----------+----------+------+--------------+
|               |5.x   |None      |Not       |          |      |              |
|BIG-IQ         |      |          |applicable|Not       |      |              |
|Centralized    +------+----------+----------+vulnerable|None  |None          |
|Management     |4.x   |None      |Not       |          |      |              |
|               |      |          |applicable|          |      |              |
+---------------+------+----------+----------+----------+------+--------------+
|BIG-IQ Cloud   |      |          |Not       |Not       |      |              |
|and            |1.x   |None      |applicable|vulnerable|None  |None          |
|Orchestration  |      |          |          |          |      |              |
+---------------+------+----------+----------+----------+------+--------------+
|F5 iWorkflow   |2.x   |None      |Not       |Not       |None  |None          |
|               |      |          |applicable|vulnerable|      |              |
+---------------+------+----------+----------+----------+------+--------------+
|LineRate       |2.x   |None      |Not       |Not       |None  |None          |
|               |      |          |applicable|vulnerable|      |              |
+---------------+------+----------+----------+----------+------+--------------+
|               |5.x   |None      |Not       |          |      |              |
|               |      |          |applicable|Not       |      |              |
|Traffix SDC    +------+----------+----------+vulnerable|None  |None          |
|               |4.x   |None      |Not       |          |      |              |
|               |      |          |applicable|          |      |              |
+---------------+------+----------+----------+----------+------+--------------+

^1The CVSSv3 score link takes you to a resource outside of AskF5, and it is
possible that the document may be removed without our knowledge.

Security Advisory Recommended Actions

If you are running a version listed in the Versions known to be vulnerable
column, you can eliminate this vulnerability by upgrading to a version listed
in the Fixes introduced in column. If the table lists only an older version
than what you are currently running, or does not list a non-vulnerable version,
then no upgrade candidate currently exists.

Mitigation

Mitigation for self IP addresses

To mitigate this issue for self IP addresses, you can use packet filters to
restrict access to trusted users. For information, refer to the following
articles:

  o K13092: Overview of securing access to the BIG-IP system
  o The Configuring Packet Filtering chapter of the TMOS: Implementations guide

    Note: For information about how to locate F5 product guides, refer to 
    K12453464: Finding product documentation on AskF5.

Mitigation for FastL4 virtual servers

For BIG-IP Virtual Edition (VE) systems that have been configured with TSO
disabled, you can mitigate this vulnerability by enabling TSO. You can enable
TSO by setting the value of the tm.tcpsegmentationoffload BigDB key to enable,
and restarting the Traffic Management Microkernel (TMM). To do so, perform the
following procedure:

Note: TSO is enabled by default. This mitigation is only applicable if you have
manually disabled TSO on BIG-IP VE.

Impact of action: Since TSO enabled is the default value for BIG-IP systems,
performing the following procedure should not have a negative impact on your
system. However, if you have disabled TSO in your environment, the impact of
the suggested mitigation will depend on the specific environment. F5 recommends
testing any such changes during a maintenance window with consideration to the
possible impact on your specific environment. Additionally, restarting TMM
temporarily interrupts traffic processing.

 1. Log in to the TMOS shell (tmsh) by typing the following command:

    tmsh

 2. Enable TSO by typing the following command:

    modify sys db tm.tcpsegmentationoffload value enable

 3. Restart TMM by typing the following command

    restart /sys service tmm

Supplemental Information

  o K15609: Overview of TCP Segmentation Offload and Large Receive Offload
  o K51812227: Understanding Security Advisory versioning
  o K41942608: Overview of Security Advisory articles
  o K4602: Overview of the F5 security vulnerability response policy
  o K4918: Overview of the F5 critical issue hotfix policy

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