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AUSCERT External Security Bulletin Redistribution
SOL22843911: F5 Path MTU Discovery vulnerability CVE-2015-7759
11 January 2016
AusCERT Security Bulletin Summary
Product: F5 BIG-IP APM
Operating System: Network Appliance
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2015-7759
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SOL22843911: F5 Path MTU Discovery vulnerability CVE-2015-7759
Security AdvisorySecurity Advisory
Original Publication Date: 01/07/2016
A remote attacker may be able to cause the Traffic Management Microkernel
(TMM) to restart using maliciously constructed ICMP packets. (CVE-2015-7759 -
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.
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
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
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.
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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