SOL18829561 - BIND vulnerability CVE-2016-2776

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 theVersions 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.

To determine the necessary upgrade path for your BIG-IQ system, you should understand the BIG-IQ product offering name changes. For more information, refer to SOL21232150: Considerations for upgrading BIG-IQ or F5 iWorkflow systems.

Mitigation

BIG-IP

To mitigate this vulnerability, you can use the DNS Caching and DNS Express features instead of BIND. In addition, to mitigate the issue on the management IP address, restrict access to that IP address to trusted hosts only.

To mitigate the issue on the self IP address, do not allow port 53 on the self IP address. If your self IP address is configured to use the default allow, you can remove that port from the list of the default allowed services.

Ensuring that TCP/UDP port 53 is not allowed as a default service (allow-service default)

1. Log in to the Traffic Management Shell (tmsh) by typing the following command:

tmsh

2. List the default services allowed by the allow-service defaultsetting, by typing the following command:

list net self-allow

The command output appears similar to the following example:

net self-allow {
defaults {
ospf:any
tcp:domain
tcp:f5-iquery
tcp:https
tcp:snmp
tcp:ssh
udp:520
udp:cap
udp:domain
udp:f5-iquery
udp:snmp
}
}

3. If TCP port 53 (tcp:53 or tcp:domain) or UDP port 53 (udp:53 or udp:domain) are listed as a default allowed port, you should delete the entries by typing the following command:

modify net self-allow defaults delete { tcp:domain udp:domain }

4. Save the configuration by typing the following command:

save sys config

Disabling the Use BIND Server on BIG-IP option on the DNS profile

To mitigate the issue on the DNS profile, you can disable the Use BIND Server on BIG-IP option by performing the following procedure:

1. Log in to the Configuration utility.
2. Navigate to DNS>Delivery >Profiles >DNSorLocal Traffic>** Profiles** >** Services** >DNS.
3. Select the applicable DNS profile.
4. From the Use BIND Server on BIG-IP option, selectDisabled. 5. ClickFinished.Important: Disabling the BIND server can impact DNS configurations that use BIND as a fallback method (return to DNS) for resolution.

BIG-IP GTM/Link Controller

Verifying whether you have configured any listener addresses to share a self IP (BIG-IP GTM/Link Controller)

Listener addresses that share a self IP address will expose the system to this vulnerability. To verify whether you have configured a listener address to share a self IP, run the following commands:

• tmsh list /net self address
• tmsh list /gtm listener address

If you have configured a listener address to share a self IP, you should reconfigure the address to use a unique IP address.

Choosing a load balancing method other than Return to DNS for the GTM pool (BIG-IP GTM)

Important: If DNS Express is not configured, BIG-IP GTM or Link Controller systems will respond toA,AAAA, andCNAMEtype DNS record queries only. Queries for other types of records, such asNSorMX, will fail.

To mitigate the issue on the GTM pool, you can use a load balancing method other than Return to DNS by performing the following procedure:

1. Log in to the Configuration utility.
2. Navigate to DNS>GSLB>** Pools.** 3. From the**Pool List **menu, select the applicable name.
3. Click the Members tab.
4. Choose a load balancing method other than Return to DNS.
5. Click Update.

BIG-IQ, Enterprise Manager or iWorkflow systems

To mitigate this vulnerability for the BIG-IQ system, the Enterprise Manager system, or the F5 iWorkflow system, you should not configure any of these systems to function as a DNS server.

Impact of action: Performing the suggested mitigation should not have a negative impact on your system.

Supplemental Information

• SOL9970: Subscribing to email notifications regarding F5 products
• SOL9957: Creating a custom RSS feed to view new and updated documents
• SOL4602: Overview of the F5 security vulnerability response policy
• SOL4918: Overview of the F5 critical issue hotfix policy
• SOL167: Downloading software and firmware from F5
• SOL17329: BIG-IP GTM name has changed to BIG-IP DNS