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

                               ESB-2016.0060
      SOL22843911: F5 Path MTU Discovery vulnerability CVE-2015-7759
                              11 January 2016

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

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

Product:           F5 BIG-IP APM
Publisher:         F5
Operating System:  Network Appliance
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2015-7759  

Original Bulletin: 
   https://support.f5.com/kb/en-us/solutions/public/k/22/sol22843911.html

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SOL22843911: F5 Path MTU Discovery vulnerability CVE-2015-7759

Security AdvisorySecurity Advisory

Original Publication Date: 01/07/2016

Vulnerability Description

A remote attacker may be able to cause the Traffic Management Microkernel 
(TMM) to restart using maliciously constructed ICMP packets. (CVE-2015-7759 -
reserved)

Virtual servers using a TCP profile configured with Congestion Metrics Cache 
enabled are affected by this vulnerability. Congestion Metrics Cache is 
enabled by default for TCP profiles.

Impact

The BIG-IP system may temporarily fail to process traffic as it recovers from
the Traffic Management Microkernel (TMM) restart, and devices configured as a
high-availability pair may fail over.

Security Issue Status

F5 Product Development has assigned ID 546140 (BIG-IP) to this vulnerability,
and has evaluated the currently supported releases for potential 
vulnerability.

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:


Product                         Versions known to be vulnerable    Versions known to be not vulnerable         Severity        Vulnerable component or feature
BIG-IP LTM                      12.0.0                             12.0.0 HF1 11.0.0 - 11.6.0 10.1.0 - 10.2.4  Severe          TMM processing of virtual servers that use a TCP profile that has Congestion Metrics Cache enabled.
BIG-IP AAM                      12.0.0                             12.0.0 HF1 11.4.0 - 11.6.0                  Severe          TMM processing of virtual servers that use a TCP profile that has Congestion Metrics Cache enabled.
BIG-IP AFM                      12.0.0                             12.0.0 HF1 11.3.0 - 11.6.0                  Severe          TMM processing of virtual servers that use a TCP profile that has Congestion Metrics Cache enabled.
BIG-IP Analytics                12.0.0                             12.0.0 HF1 11.0.0 - 11.6.0                  Severe          TMM processing of virtual servers that use a TCP profile that has Congestion Metrics Cache enabled.
BIG-IP APM                      12.0.0                             12.0.0 HF1 11.0.0 - 11.6.0 10.1.0 - 10.2.4  Severe          TMM processing of virtual servers that use a TCP profile that has Congestion Metrics Cache enabled.
BIG-IP ASM                      12.0.0                             12.0.0 HF1 11.0.0 - 11.6.0 10.1.0 - 10.2.4  Severe          TMM processing of virtual servers that use a TCP profile that has Congestion Metrics Cache enabled.
BIG-IP DNS                      None                               12.0.0                                      Not vulnerable  None
BIG-IP Edge Gateway             None                               11.0.0 - 11.3.0 10.1.0 - 10.2.4             Not vulnerable  None
BIG-IP GTM                      None                               11.0.0 - 11.6.0 10.1.0 - 10.2.4             Not vulnerable  None
BIG-IP Link Controller          12.0.0                             12.0.0 HF1 11.0.0 - 11.6.0 10.1.0 - 10.2.4  Severe          TMM processing of virtual servers that use a TCP profile that has Congestion Metrics Cache enabled.
BIG-IP PEM                      12.0.0                             12.0.0 HF1 11.3.0 - 11.6.0                  Severe          TMM processing of virtual servers that use a TCP profile that has Congestion Metrics Cache enabled.
BIG-IP PSM                      None                               11.0.0 - 11.4.1 10.1.0 - 10.2.4             Not vulnerable  None
BIG-IP WebAccelerator           None                               11.0.0 - 11.3.0 10.1.0 - 10.2.4             Not vulnerable  None
BIG-IP WOM                      None                               11.0.0 - 11.3.0 10.1.0 - 10.2.4             Not vulnerable  None
ARX                             None                               6.0.0 - 6.4.0                               Not vulnerable  None
Enterprise Manager              None                               3.0.0 - 3.1.1                               Not vulnerable  None
FirePass                        None                               7.0.0 6.0.0 - 6.1.0                         Not vulnerable  None
BIG-IQ Cloud                    None                               4.0.0 - 4.5.0                               Not vulnerable  None
BIG-IQ Device                   None                               4.2.0 - 4.5.0                               Not vulnerable  None
BIG-IQ Security                 None                               4.0.0 - 4.5.0                               Not vulnerable  None
BIG-IQ ADC                      None                               4.5.0                                       Not vulnerable  None
BIG-IQ Centralized Management   None                               4.6.0                                       Not vulnerable  None
BIG-IQ Cloud and Orchestration  None                               1.0.0                                       Not vulnerable  None
LineRate                        None                               2.5.0 - 2.6.1                               Not vulnerable  None
F5 WebSafe                      None                               1.0.0                                       Not vulnerable  None
Traffix SDC                     None                               4.0.0 - 4.4.0 3.3.2 - 3.5.1                 Not vulnerable  None



Vulnerability 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 Versions known to be not vulnerable 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.

F5 responds to vulnerabilities in accordance with the Severity values 
published in the previous table. The Severity values and other security 
vulnerability parameters are defined in SOL4602: Overview of the F5 security 
vulnerability response policy.

To mitigate this vulnerability, you can disable the Congestion Metrics Cache 
setting (cmetrics-cache) for all TCP profiles on the BIG-IP system. To do so,
use one of the following options:

Using the Configuration utility, navigate to the Local Traffic > Profiles > 
Protocol > TCP page and select the profile you want to edit, and clear the 
Congestion Metrics Cache check box.

- From the command line, use the following command syntax:

tmsh modify ltm profile tcp <profile_name> cmetrics-cache disabled

In the previous syntax, <profile_name> is the name of the tcp profile for 
which you are disabling Congestion Metrics Cache.

Impact of action: The impact of the suggested mitigation depends on the 
specific environment. Disabling Congestion Metrics Cache in the TCP profiles 
may result in performance degradation, depending on network conditions. F5 
recommends that you test any such changes during a maintenance window with 
consideration to the possible impact on your specific environment.

Alternatively, if Path MTU Discovery (PMTU) functionality is not required, you
could consider the following alternative actions:

Block the ICMP Type 3 Code 4 (Fragmentation Needed) packets before they reach
the BIG-IP system, by using an upstream firewall or BIG-IP AFM system.

Block all ICMP traffic using an upstream firewall or the BIG-IP AFM system.

Important: Blocking ICMP traffic prevents PMTU from functioning, and may 
impact other network services that rely on ICMP. F5 recommends that you 
evaluate the potential impact of blocking ICMP traffic in your environment. 
For information about blocking ICMP traffic with the BIG-IP AFM module, refer
to the Deploying the BIG-IP Network Firewall in ADC Mode chapter of the BIG-IP
Network Firewall: Policies and Implementations guide, and browse the Adding a
firewall rule to deny ICMP section.

Note: You cannot use BIG-IP packet filters to mitigate this vulnerability.

Supplemental Information

SOL9970: Subscribing to email notifications regarding F5 products

SOL9957: Creating a custom RSS feed to view new and updated documents

SOL4918: Overview of the F5 critical issue hotfix policy

SOL167: Downloading software and firmware from F5

SOL13123: Managing BIG-IP product hotfixes (11.x - 12.x)

SOL9502: BIG-IP hotfix matrix

SOL12343: The SYN retransmission interval may vary when the Congestion Metrics
Cache setting is enabled in the TCP profile

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