Protect yourself against future threats.
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AUSCERT External Security Bulletin Redistribution
ESB-2019.3907
BIND security update for spoofing and DoS
18 October 2019
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AusCERT Security Bulletin Summary
---------------------------------
Product: BIND
Publisher: ISC
Operating System: UNIX variants (UNIX, Linux, OSX)
Impact/Access: Denial of Service -- Remote/Unauthenticated
Provide Misleading Information -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2019-6476 CVE-2019-6475
Original Bulletin:
https://lists.isc.org/pipermail/bind-announce/2019-October.txt
Comment: This bulletin contains two (2) BIND security advisories.
- --------------------------BEGIN INCLUDED TEXT--------------------
CVE: CVE-2019-6475
Document version: 2.0
Posting date: 16 October 2019
Program impacted: BIND
Versions affected: BIND 9.14.0 -> 9.14.6. Also releases 9.15.0 ->
9.15.4 of the BIND 9.15 development branch.
Severity: Medium
Exploitable: Remotely
Description:
Mirror zones are a BIND feature allowing recursive servers to
pre-cache zone data provided by other servers. A mirror zone is
similar to a zone of type secondary, except that its data is
subject to DNSSEC validation before being used in answers, as
if it had been looked up via traditional recursion, and when
mirror zone data cannot be validated, BIND falls back to using
traditional recursion instead of the mirror zone. However, an
error in the validity checks for the incoming zone data can allow
an on-path attacker to replace zone data that was validated with
a configured trust anchor with forged data of the attacker's
choosing.
The mirror zone feature is most often used to serve a local copy
of the root zone. If an attacker was able to insert themselves
into the network path between a recursive server using a mirror
zone and a root name server, this vulnerability could then be
used to cause the recursive server to accept a copy of falsified
root zone data.
Impact:
An on-path attacker who manages to successfully exploit this
vulnerability can replace the mirrored zone (usually the root)
with data of their own choosing, effectively bypassing DNSSEC
protection.
CVSS Score: 5.9
CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
For more information on the Common Vulnerability Scoring System and
to obtain your specific environmental score please visit:
https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N.
Workarounds:
The vulnerability can be avoided by not using mirror zones.
Active exploits:
None known.
Solution:
Upgrade to the patched release most closely related to your
current version of BIND:
+ BIND 9.14.7
+ BIND 9.15.5
Document revision history:
1.0 Early Notification, 09 October 2019
2.0 Public Disclosure, 16 October 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-2019-6476
Document version: 2.0
Posting date: 16 October 2019
Program impacted: BIND
Versions affected: BIND 9.14.0 -> 9.14.6. Also releases 9.15.0 ->
9.15.4 of the BIND 9.15 development branch.
Severity: Medium
Exploitable: Remotely
Description:
A defect in code added to support QNAME minimization can cause
named to exit with an assertion failure if a forwarder returns
a referral rather than resolving the query.
Impact:
An attacker who manages to deliberately trigger this condition
on a server which is performing recursion can cause named to
exit, denying service to clients.
CVSS Score: 5.9
CVSS Vector: CVSS:3.1/AV:N/AC:H/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://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.
Workarounds:
Servers which have QNAME minimization turned on are potentially
vulnerable to this defect if they are running an affected version
of BIND. The vulnerability can be avoided by disabling QNAME
minimization using "qname-minimization disabled;" in the global
options section of named.conf (Note: the default value for the
qname-minimization setting in the 9.14 and 9.15 branches is
"relaxed". To make use of this workaround it must be explicitly
disabled.)
Active exploits:
None known.
Solution:
Upgrade to the patched release most closely related to your
current version of BIND:
+ BIND 9.14.7
+ BIND 9.15.5
Document revision history:
1.0 Early Notification, 09 October 2019
2.0 Public Disclosure, 16 October 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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