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===========================================================================
             AUSCERT External Security Bulletin Redistribution

                               ESB-2019.1408
           Multiple vulnerabilities have been identified in BIND
                               26 April 2019

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

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

Product:           BIND
Publisher:         ISC
Operating System:  UNIX variants (UNIX, Linux, OSX)
                   Windows
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2019-6468 CVE-2019-6467 CVE-2018-5743

Reference:         ESB-2019.1405

Original Bulletin: 
   https://kb.isc.org/docs/cve-2018-5743
   https://kb.isc.org/docs/cve-2019-6467
   https://kb.isc.org/docs/cve-2019-6468

Comment: This bulletin contains three (3) ISC security advisories.

- --------------------------BEGIN INCLUDED TEXT--------------------

CVE:                 CVE-2018-5743
Document version:    2.0
Posting date:        24 April 2019
Program impacted:    BIND
Versions affected:   BIND 9.9.0 -> 9.10.8-P1, 9.11.0 -> 9.11.6,
                     9.12.0 -> 9.12.4, 9.14.0. BIND 9 Supported Preview
                     Edition versions 9.9.3-S1 -> 9.11.5-S3, and 9.11.5-S5.
                     Versions 9.13.0 -> 9.13.7 of the 9.13 development
branch
                     are also affected. Versions prior to BIND 9.9.0
have not
                     been evaluated for vulnerability to CVE-2018-5743.
Severity:            High
Exploitable:         Remotely

Description:

   By design, BIND is intended to limit the number of TCP clients
   that can be connected at any given time. The number of allowed
   connections is a tunable parameter which, if unset, defaults to
   a conservative value for most servers. Unfortunately, the code
   which was intended to limit the number of simultaneous connections
   contains an error which can be exploited to grow the number of
   simultaneous connections beyond this limit.

Impact:

   By exploiting the failure to limit simultaneous TCP connections,
   an attacker can deliberately exhaust the pool of file descriptors
   available to named, potentially affecting network connections
   and the management of files such as log files or zone journal
   files.

   In cases where the named process is not limited by OS-enforced
   per-process limits, this could additionally potentially lead to
   exhaustion of all available free file descriptors on that system.

CVSS Score:          7.5
CVSS Vector:         CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

For more information on the Common Vulnerability Scoring System and
to obtain your specific environmental score please visit:
https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Workarounds:

   None.

Active exploits:

   No known deliberate exploits, but the situation may occur
   accidentally on busy servers.

   It is possible for operators to mistakenly believe that their
   configured (or default) limit is sufficient for their typical
   operations, when in fact it is not. Following an upgrade to a
   version that effectively applies limits, named may deny connections
   which were previously improperly permitted. Operators can monitor
   their logs for rejected connections, keep an eye on "rndc status"
   reports of simultaneous connections, or use other tools to monitor
   whether the now-effective limits are causing problems for
   legitimate clients. Should this be the case, increasing the value
   of the tcp-clients setting in named.conf to an appropriate value
   would be recommended.

Solution:

   Upgrade to a version of BIND containing a fix for the ineffective
   limits.

   -  BIND 9.11.6-P1
   -  BIND 9.12.4-P1
   -  BIND 9.14.1

   BIND Supported Preview Edition is a special feature preview
   branch of BIND provided to eligible ISC support customers.

   -  BIND 9.11.5-S6
   -  BIND 9.11.6-S1

Acknowledgements:

   ISC would like to thank AT&T for helping us to discover this
   issue.

Document revision history:

   1.0 Advance Notification, 16 January 2019
   1.1 Recall due to error in original fix, 17 January 2019
   1.3 Replacement fix delivered to Advance Notification customers, 15
April 2019
   1.4 Corrected Versions affected and Solution, 16 April 2019
   1.5 Added reference to BIND 9.11.6-S1
   2.0 Public disclosure, 24 April 2019

Related documents:

   See our BIND 9 Security Vulnerability Matrix for a complete
   listing of security vulnerabilities and versions affected.

Do you still have questions? Questions regarding this advisory
should go to security-officer@isc.org. To report a new issue, please
encrypt your message using security-officer@isc.org's PGP key which
can be found here:
   https://www.isc.org/downloads/software-support-policy/openpgp-key
If you are unable to use encrypted email, you may also report new
issues at: https://www.isc.org/community/report-bug/.

Note:

   ISC patches only currently supported versions. When possible we
   indicate EOL versions affected. (For current information on which
   versions are actively supported, please see
   https://www.isc.org/downloads/.)

ISC Security Vulnerability Disclosure Policy:

   Details of our current security advisory policy and practice can
   be found in the ISC Software Defect and Security Vulnerability
   Disclosure Policy.

Legal Disclaimer:

   Internet Systems Consortium (ISC) is providing this notice on
   an "AS IS" basis. No warranty or guarantee of any kind is expressed
   in this notice and none should be implied. ISC expressly excludes
   and disclaims any warranties regarding this notice or materials
   referred to in this notice, including, without limitation, any
   implied warranty of merchantability, fitness for a particular
   purpose, absence of hidden defects, or of non-infringement. Your
   use or reliance on this notice or materials referred to in this
   notice is at your own risk. ISC may change this notice at any
   time. A stand-alone copy or paraphrase of the text of this
   document that omits the document URL is an uncontrolled copy.
   Uncontrolled copies may lack important information, be out of
   date, or contain factual errors.

- ---

CVE:                 CVE-2019-6467
Document version:    2.0
Posting date:        24 April 2019
Program impacted:    BIND
Versions affected:   BIND 9.12.0-> 9.12.4, 9.14.0. Also affects all releases
                     in the 9.13 development branch.
Severity:            Medium
Exploitable:         Remotely

Description:

   A programming error in the nxdomain-redirect feature can cause
   an assertion failure in query.c if the alternate namespace used
   by nxdomain-redirect is a descendant of a zone that is served
   locally.

   The most likely scenario where this might occur is if the server,
   in addition to performing NXDOMAIN redirection for recursive
   clients, is also serving a local copy of the root zone or using
   mirroring to provide the root zone, although other configurations
   are also possible.

Impact:

   An attacker who can deliberately trigger the condition on a
   server with a vulnerable configuration can cause BIND to exit,
   denying service to other clients.

CVSS Score:          5.9
CVSS Vector:         CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

For more information on the Common Vulnerability Scoring System and
to obtain your specific environmental score please visit:
https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.

Workarounds:

   Exploitation of this defect can be effectively prevented by
   disabling the nxdomain-redirect feature in the nameserver's
   configuration.

Active exploits:

   None known.

Solution:

   Upgrade to the patched release most closely related to your current
version of BIND:

   -  BIND 9.12.4-P1
   -  BIND 9.14.1

Document revision history:

   1.0 Early Notification, 15 April 2019
   1.1 Removed BIND 9.11.6-P1 from Solution version list
   2.0 Public Disclosure, 24 April 2019

Related documents:

   See our BIND 9 Security Vulnerability Matrix for a complete
   listing of security vulnerabilities and versions affected.

Do you still have questions? Questions regarding this advisory
should go to security-officer@isc.org. To report a new issue, please
encrypt your message using security-officer@isc.org's PGP key which
can be found here:
   https://www.isc.org/downloads/software-support-policy/openpgp-key
If you are unable to use encrypted email, you may also report new
issues at: https://www.isc.org/community/report-bug/.

Note:

   ISC patches only currently supported versions. When possible we
   indicate EOL versions affected. (For current information on which
   versions are actively supported, please see
   https://www.isc.org/downloads/.)

ISC Security Vulnerability Disclosure Policy:

   Details of our current security advisory policy and practice can
   be found in the ISC Software Defect and Security Vulnerability
   Disclosure Policy.

Legal Disclaimer:

   Internet Systems Consortium (ISC) is providing this notice on
   an "AS IS" basis. No warranty or guarantee of any kind is expressed
   in this notice and none should be implied. ISC expressly excludes
   and disclaims any warranties regarding this notice or materials
   referred to in this notice, including, without limitation, any
   implied warranty of merchantability, fitness for a particular
   purpose, absence of hidden defects, or of non-infringement. Your
   use or reliance on this notice or materials referred to in this
   notice is at your own risk. ISC may change this notice at any
   time. A stand-alone copy or paraphrase of the text of this
   document that omits the document URL is an uncontrolled copy.
   Uncontrolled copies may lack important information, be out of
   date, or contain factual errors.

- ---

CVE:                 CVE-2019-6468
Document version:    2.0
Posting date:        24 April 2019
Program impacted:    BIND
Versions affected:   BIND Supported Preview Edition version
                     9.10.5-S1 -> 9.11.5-S5. ONLY BIND Supported
                     Preview Edition releases are affected.
Severity:            Medium
Exploitable:         Remotely

Description:

   In BIND Supported Preview Edition, an error in the nxdomain-redirect
   feature can occur in versions which support EDNS Client Subnet
   (ECS) features. In those versions which have ECS support, enabling
   nxdomain-redirect is likely to lead to BIND exiting due to
   assertion failure.

Impact:

   If nxdomain-redirect is enabled (via configuration) in a vulnerable
   BIND release, a malicious party can cause BIND to exit by
   deliberately triggering the bug.

CVSS Score:          5.9
CVSS Vector:         CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

For more information on the Common Vulnerability Scoring System and
to obtain your specific environmental score please visit:
https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.

Workarounds:

   Exploitation of this defect can be effectively prevented by
   disabling the nxdomain-redirect feature in the nameserver's
   configuration.

Active exploits:

   None known.

Solution:

   Upgrade to the patched release most closely related to your
   current version of BIND:

   BIND Supported Preview Edition is a special feature preview
   branch of BIND provided to eligible ISC support customers.

   -  BIND 9.11.5-S6
   -  BIND 9.11.6-S1

Document revision history:

   1.0 Early Notification, 15 April 2019
   1.1 Added reference to BIND 9.11.6-S1 in Solution section
   2.0 Public Disclosure, 24 April 2019

Related documents:

See our BIND 9 Security Vulnerability Matrix for a complete listing
of security vulnerabilities and versions affected.

Do you still have questions? Questions regarding this advisory
should go to security-officer@isc.org. To report a new issue, please
encrypt your message using security-officer@isc.org's PGP key which
can be found here:
   https://www.isc.org/downloads/software-support-policy/openpgp-key
If you are unable to use encrypted email, you may also report new
issues at: https://www.isc.org/community/report-bug/.

Note:

   ISC patches only currently supported versions. When possible we
   indicate EOL versions affected. (For current information on which
   versions are actively supported, please see
   https://www.isc.org/downloads/.)

ISC Security Vulnerability Disclosure Policy:

   Details of our current security advisory policy and practice can
   be found in the ISC Software Defect and Security Vulnerability
   Disclosure Policy.

Legal Disclaimer:

   Internet Systems Consortium (ISC) is providing this notice on
   an "AS IS" basis. No warranty or guarantee of any kind is expressed
   in this notice and none should be implied. ISC expressly excludes
   and disclaims any warranties regarding this notice or materials
   referred to in this notice, including, without limitation, any
   implied warranty of merchantability, fitness for a particular
   purpose, absence of hidden defects, or of non-infringement. Your
   use or reliance on this notice or materials referred to in this
   notice is at your own risk. ISC may change this notice at any
   time. A stand-alone copy or paraphrase of the text of this
   document that omits the document URL is an uncontrolled copy.
   Uncontrolled copies may lack important information, be out of
   date, or contain factual errors.

- --------------------------END INCLUDED TEXT--------------------

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