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             AUSCERT External Security Bulletin Redistribution

                              ESB-2020.2136.3
                     BIND vulnerability CVE-2020-8619
                              28 August 2020

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

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

Product:           F5 Big-IP Products
Publisher:         F5 Networks
Operating System:  Network Appliance
Impact/Access:     Denial of Service -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2020-8619  

Reference:         ESB-2020.2105
                   ESB-2020.2104

Original Bulletin: 
   https://support.f5.com/csp/article/K19807532

Revision History:  August 28 2020: Patch released for the 15.1.x branch
                                   but not 15.0.x
                   August 20 2020: A fix is available for the 14.x branch
                   June   19 2020: Initial Release

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K19807532:BIND vulnerability CVE-2020-8619

Security Advisory

Original Publication Date: 19 Jun, 2020

Security Advisory Description

The asterisk character ("*") is allowed in DNS zone files, where it is most
commonly present as a wildcard at a terminal node of the Domain Name System
graph. However, the RFCs do not require and BIND does not enforce that an
asterisk character be present only at a terminal node.

A problem can occur when an asterisk is present in an empty non-terminal
location within the DNS graph. If such a node exists, after a series of
queries, named can reach an inconsistent state that results in the failure of
an assertion check in rbtdb.c, followed by the program exiting due to the
assertion failure. (CVE-2020-8619)

Impact

You encounter this defect when you have both of the following conditions:

  o A nameserver provides authoritative service for one or more zones.
  o At least one zone contains an empty non-terminal entry containing an
    asterisk character.

A would-be attacker who is allowed to change zone content could, theoretically,
introduce such a record in order to exploit this condition to cause
denial-of-service (DoS); however, the use of this vector is unlikely because
any such attack requires a significant privilege-level and is easily traceable.

BIND versions from 9.11.14 through 9.11.19 are impacted.

Security Advisory Status

F5 Product Development has assigned ID 917005 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  |15.1.0    |15.1.0.5  |           |      |          |
|                  |15.x  |15.0.0 -  |None      |           |      |          |
|                  |      |15.1.0    |          |           |      |          |
|                  +------+----------+----------+           |      |          |
|                  |14.x  |14.1.0 -  |14.1.2.7  |           |      |          |
|BIG-IP (LTM, AAM, |      |14.1.2    |          |           |      |          |
|AFM, Analytics,   +------+----------+----------+           |      |          |
|APM, ASM, DNS,    |13.x  |13.1.0 -  |None      |Medium     |4.3   |BIND      |
|FPS, GTM, Link    |      |13.1.3    |          |           |      |          |
|Controller, PEM)  +------+----------+----------+           |      |          |
|                  |12.x  |12.1.0 -  |None      |           |      |          |
|                  |      |12.1.5    |          |           |      |          |
|                  +------+----------+----------+           |      |          |
|                  |11.x  |11.6.1 -  |None      |           |      |          |
|                  |      |11.6.5    |          |           |      |          |
+------------------+------+----------+----------+-----------+------+----------+
|                  |7.x   |None      |Not       |           |      |          |
|                  |      |          |applicable|           |      |          |
|                  +------+----------+----------+Not        |      |          |
|BIG-IQ Centralized|6.x   |None      |Not       |vulnerable^|None  |None      |
|Management        |      |          |applicable|2          |      |          |
|                  +------+----------+----------+           |      |          |
|                  |5.x   |None      |Not       |           |      |          |
|                  |      |          |applicable|           |      |          |
+------------------+------+----------+----------+-----------+------+----------+
|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.

^2The specified products contain the affected code. However, F5 identifies the
vulnerability status as Not vulnerable because the attacker cannot exploit the
code in default, standard, or recommended configurations.

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.

Mitigation

To mitigate this vulnerability, when you configure a non-terminal location for
any zones in your zone file, avoid using an empty non-terminal record
containing an asterisk character. The following example displays an empty
non-terminal record that could trigger this vulnerability:

foo.*.example.com

For more information about empty non-terminal records, refer to What is an
Empty Non-Terminal.

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