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             AUSCERT External Security Bulletin Redistribution

             BIG-IP & BIG-IQ BIND vulnerability CVE-2020-8617
                               25 June 2020


        AusCERT Security Bulletin Summary

Product:           BIG-IP
Publisher:         F5 Networks
Operating System:  Network Appliance
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2020-8617  

Reference:         ESB-2020.1820

Original Bulletin: 

Revision History:  June 25 2020: Vendor released minor update
                   June 19 2020: Vendor updated Product Status Advisory table
                   June 12 2020: Fixes introduced for BIG-IP
                   June  1 2020: Vendor published mitigation information
                   May  25 2020: Initial Release

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K05544642:BIND vulnerability CVE-2020-8617

Security Advisory

Original Publication Date: 21 May, 2020

Latest   Publication Date: 24 Jun, 2020

Security Advisory Description

Using a specially-crafted message, an attacker may potentially cause a BIND
server to reach an inconsistent state if the attacker knows (or successfully
guesses) the name of a TSIG key used by the server. Since BIND, by default,
configures a local session key even on servers whose configuration does not
otherwise make use of it, almost all current BIND servers are vulnerable. In
releases of BIND dating from March 2018 and after, an assertion check in tsig.c
detects this inconsistent state and deliberately exits. Prior to the
introduction of the check the server would continue operating in an
inconsistent state, with potentially harmful results. (CVE-2020-8617)


An attacker can exploit this vulnerability to trigger an assertion failure,
resulting in a denial of service to clients.

Security Advisory Status

F5 Product Development has assigned IDs 909237 (BIG-IP) and 909237-8 (BIG-IQ)
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, point releases, or
hotfixes that address the vulnerability, refer to the following table. For more
information about security advisory versioning, refer to K51812227:
Understanding Security Advisory versioning.

|                   |      |Versions  |Fixes     |          |CVSSv3|Vulnerable|
|Product            |Branch|known to  |introduced|Severity  |score^|component |
|                   |      |be        |in        |          |1     |or feature|
|                   |      |vulnerable|          |          |      |          |
|                   |15.x  |15.0.0 -  |  |          |      |          |
|                   |      |15.1.0    |          |          |      |          |
|                   +------+----------+----------+          |      |          |
|                   |14.x  |14.1.0 -  |  |          |      |          |
|BIG-IP (LTM, AAM,  |      |14.1.2    |          |          |      |          |
|AFM, Analytics,    +------+----------+----------+          |      |          |
|APM, ASM, DNS, FPS,|13.x  |13.1.0 -  |  |High      |7.5   |BIND      |
|GTM, Link          |      |13.1.3    |          |          |      |          |
|Controller, PEM)   +------+----------+----------+          |      |          |
|                   |12.x  |12.1.0 -  |None      |          |      |          |
|                   |      |12.1.5    |          |          |      |          |
|                   +------+----------+----------+          |      |          |
|                   |11.x  |11.6.1 -  |  |          |      |          |
|                   |      |11.6.5    |          |          |      |          |
|                   |7.x   |7.0.0 -   |None      |          |      |          |
|                   |      |7.1.0     |          |          |      |          |
|                   +------+----------+----------+          |      |          |
|BIG-IQ Centralized |6.x   |6.0.0 -   |None      |High      |7.5   |BIND      |
|Management         |      |6.1.0     |          |          |      |          |
|                   +------+----------+----------+          |      |          |
|                   |5.x   |5.3.0 -   |None      |          |      |          |
|                   |      |5.4.0     |          |          |      |          |
|Traffix SDC        |5.x   |None      |Not       |Not       |None  |None      |
|                   |      |          |applicable|vulnerable|      |          |

^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.


The following mitigation options are available for the BIG-IP and BIG-IQ

  o BIG-IP
  o BIG-IQ


To mitigate this vulnerability for the BIG-IP system, perform the following

  o When there is no requirement to use the BIG-IP DNS service, you should
    secure the self IP addresses on the BIG-IP system by using the port
    lockdown feature to deny access to DNS services on the system. To do so,
    refer to the Using the Configuration utility to modify port lockdown
    settings for a specific self IP procedure in K17333: Overview of port
    lockdown behavior (12.x - 15.x).

    The management IP address of the BIG-IP system does not respond to DNS

BIG-IP DNS, BIG-IP GTM, and Link Controller

To mitigate this vulnerability, you can configure the DNS profile to not
forward queries to BIND by setting Use BIND Server on BIG-IP to Disabled. For
queries that do not need to be processed further in BIND, if there is no pool
assigned to the Virtual Server processing DNS request, set Unhandled Query
Actions to any setting other than Allow (for example, Drop or Hint). For
Virtual Server processing DNS requests assigned with a pool of DNS Servers or
configured for DNS Caching , set Unhandled Query Actions to Allow. Setting
Unhandled Query Actions to Allow will allow further processing of the DNS
requests to the pool of DNS Servers. To do so, perform the following procedure:

Important: Disabling the BIND server can affect DNS configurations that use
BIND as a fallback method (return to DNS) for resolution.

 1. Log in to the Configuration utility.
 2. Go to Local Traffic > Profiles > Services > DNS.
 3. Select the applicable DNS profile.
 4. For Use BIND Server on BIG-IP, select Disabled.
 5. Set Unhandled Query Actions:
       If you have a virtual server which is processing DNS requests assigned
        with a pool of DNS servers or configured for DNS caching, for Unhandled
        Query Actions select Allow.
       If there is no pool assigned to the virtual server, for Unhandled Query
        Actions, select a setting other than Allow. For example, select Drop 
        or Hint.
 6. Select Update.


When there is no requirement to use the BIG-IP DNS service, you should secure
the self IP addresses on the BIG-IQ system by using the port lockdown feature
to deny access to DNS services on the system. To do so, refer to K39403510:
Managing the port lockdown configuration on the BIG-IQ system.

The management IP address of the BIG-IQ system does not respond to DNS queries.

Supplemental Information

o K51812227: Understanding Security Advisory versioning
  o K41942608: Overview of AskF5 Security Advisory articles
  o K4602: Overview of the F5 security vulnerability response policy
  o K4918: Overview of the F5 critical issue hotfix policy
  o K9502: BIG-IP hotfix and point release matrix
  o K13123: Managing BIG-IP product hotfixes (11.x - 15.x)
  o K15106: Managing BIG-IQ product hotfixes
  o K15113: BIG-IQ hotfix and point release matrix
  o K167: Downloading software and firmware from F5
  o K9970: Subscribing to email notifications regarding F5 products
  o K9957: Creating a custom RSS feed to view new and updated documents

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