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AUSCERT External Security Bulletin Redistribution
ESB-2014.2512
SOL15931: Unbound vulnerability CVE-2014-8602
24 December 2014
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AusCERT Security Bulletin Summary
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Product: BIG-IP LTM
Publisher: F5 Networks
Operating System: Network Appliance
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2014-8602
Reference: ESB-2014.2444
ESB-2014.2354
Original Bulletin:
https://support.f5.com/kb/en-us/solutions/public/15000/900/sol15931.html
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SOL15931: Unbound vulnerability CVE-2014-8602
Security Advisory
Original Publication Date: 12/23/2014
Description
iterator.c in NLnet Labs Unbound before 1.5.1 does not limit delegation
chaining, which allows remote attackers to cause a denial of service (memory
and CPU consumption) via a large or infinite number of referrals.
(CVE-2014-8602)
Impact
An attacker with a properly configured authority server could cause a
denial-of-service using a crafted DNS recursive query, designed to follow an
endless series of delegations.
Status
F5 Product Development has assigned ID 492368 (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 Vulnerable component or feature
BIG-IP LTM 11.2.0 - 11.6.0 11.5.1 HF7 DNS Cache feature and BIND
11.0.0 - 11.1.0
10.1.0 - 10.2.4
Recommended action
If the previous table lists a version in the Versions known to be not
vulnerable column, you can eliminate this vulnerability by upgrading to the
listed version. If the listed version is older than the version you are
currently running, or if the table does not list any version in the column,
then no upgrade candidate currently exists.
F5 is responding to this vulnerability as determined by the parameters defined
in SOL4602: Overview of the F5 security vulnerability response policy.
To mitigate this vulnerability, you can perform one or both of the following
procedures, depending on the features that you are using:
* If you are using the DNS Cache feature, and the Resolver Type is set to
Resolver or Validating Resolver, then you can create a new DNS Cache with the
Resolver Type as Transparent to prevent the system from making recursive DNS
queries.
Note: You can only set the Resolver Type when you initially create the DNS
Cache. To change the type, you must create a new DNS Cache and assign it to
the DNS profile.
* If you have enabled recursion in your BIND configuration, you can prevent the
BIG-IP system from performing recursive DNS queries by disabling recursion.
Important: By default, recursion is not enabled in the BIND configuration on
BIG-IP systems.
To do so, perform the following procedures:
* Disabling BIND recursion if it has been manually enabled
* Configuring the DNS Cache Resolver Type as Transparent
* Disabling DNS Cache in the DNS Profile
Disabling BIND recursion if it has been manually enabled
* Determining if recursion has been manually enabled on the system
* Disabling recursion
Determining if recursion has been manually enabled on the system
To determine if recursion has been manually enabled on the system, perform the
following procedure:
1. Log in to the BIG-IP command line.
2. Type the following command:
grep recursion /var/named/config/named.conf
3. If the command returns the following response, recursion has been enabled, and
you should perform the following Disabling recursion procedure.
recursion yes;
If the command returns the following response, recursion has not been enabled,
and the system is not vulnerable.
recursion no;
Disabling recursion
To mitigate this vulnerability, you can turn recursion off in the named.conf
file. To do so, perform the following procedure:
Impact of action: This modification will require a change to your
configuration, and should be tested in an appropriate environment prior to
implementation.
1. Log in to the BIG-IP command line.
2. Change directories to the /var/named/config directory by typing the following
command:
cd /var/named/config
3. Create a backup of the named.conf file by typing the following command:
cp named.conf named.conf.SOL15931
4. To edit the named.conf file, locate the recursion option, for example:
recursion yes;
5. Change the recursion option to no, for example:
recursion no;
6. Save the changes to the named.conf file.
7. Restart named to allow the changes to reload by typing the following command:
bigstart restart named
Configuring the DNS Cache Resolver Type as Transparent
* Creating a new Transparent DNS Cache
* Assigning the new DNS Cache to your DNS profile
Creating a new Transparent DNS Cache
Impact of action: This modification includes creating a new DNS Cache. Once
assigned to the DNS profile, any previously cached responses associated to the
old DNS Cache will be gone, and will need to be re-cached. All changes should
be tested in an appropriate environment prior to implementation.
1. Log in to the BIG-IP Configuration utility.
2. Expand the DNS menu.
3. Click Caches.
4. Click Create.
5. From the Resolver Type menu, select Transparent (None).
6. Fill in the remaining fields as desired.
7. Click Finished.
Assigning the new DNS Cache to the DNS profile
Impact of action: This modification includes creating a new DNS Cache. Once
assigned to the DNS profile, any previously cached responses associated to the
old DNS Cache will be gone, and will need to be re-cached. All changes should
be tested in an appropriate environment prior to implementation.
1. Log in to the BIG-IP Configuration utility.
2. Expand the Local Traffic menu.
3. Click Profiles.
4. From the Services menu, select DNS.
5. Click the name of the DNS profile that is associated with the affected virtual
server or listener.
6. From the DNS Cache Name menu, select the name of the DNS Cache you created in
the previous procedure, Create a new Transparent DNS Cache.
7. Click Update.
Disabling DNS Cache in the DNS Profile
Impact of workaround: The BIG-IP system will not cache DNS responses.
1. Log in to the BIG-IP Configuration utility.
2. Expand the Local Traffic menu.
3. Click Profiles.
4. From the Services menu, select DNS.
5. Click the name of the DNS profile that is associated with the affected virtual
server or listener.
6. From the DNS Cache menu, select Disabled.
7. Click Update.
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
SOL13123: Managing BIG-IP product hotfixes (11.x)
SOL9502: BIG-IP hotfix matrix
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