CVE-2017-3140: An error processing RPZ rules can cause named to loop
endlessly after handling a query
CVE: CVE-2017-3140
Document Version: 2.0
Posting date: 14 June 2017
Program Impacted: BIND
Versions affected: 9.9.10, 9.10.5, 9.11.0->9.11.1, 9.9.10-S1, 9.10.5-S1
Severity: Medium
Exploitable: Remotely
Description:
If named is configured to use Response Policy Zones (RPZ) an error
processing some rule types can lead to a condition where BIND will
endlessly loop while handling a query.
Impact:
A server is potentially vulnerable to degradation of service if
1. the server is configured to use RPZ,
2. the server uses NSDNAME or NSIP policy rules, and
3. an attacker can cause the server to process a specific query
Successful exploitation of this condition will cause named to enter
a state where it continues to loop while processing the query
without ever reaching an end state. While in this state, named
repeatedly queries the same sets of authoritative nameservers and
this behavior will usually persist indefinitely beyond the normal
client query processing timeout. By triggering this condition
multiple times, an attacker could cause a deliberate and substantial
degradation in service.
Operators of servers that meet the above conditions 1. and 2. may
also accidentally encounter this defect during normal operation. It
is for this reason that the decision was made to issue this advisory
despite its low CVSS score.
CVSS Score: 3.7
CVSS Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
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:L
Workarounds:
Only the NSDNAME and NSIP RPZ rule types can cause this condition to
occur. You can work around this vulnerability if you are able to
express your desired policy while avoiding NSDNAME or NSIP rules,
otherwise it is advised that you upgrade to a version which corrects
the defect.
Active exploits:
No known active exploits but we have received reports of servers
accidentally encountering this defect during operation.
Solution:
Upgrade to the patched release most closely related to your current
version of BIND. These can all be downloaded from
http://www.isc.org/downloads.
- BIND 9 version 9.9.10-P1
- BIND 9 version 9.10.5-P1
- BIND 9 version 9.11.1-P1
BIND Supported Preview Edition is a special feature preview branch
of BIND provided to eligible ISC support customers.
- BIND 9 version 9.9.10-S2
- BIND 9 version 9.10.5-S2
Acknowledgements:
ISC would like to thank Oli Schacher of Switch for bringing this
defect to our attention.
Document Revision History:
1.0 Advance Notification 06 June, 2017
2.0 Public Announcement 14 June, 2017
Related Documents:
See our BIND9 Security Vulnerability Matrix at
https://kb.isc.org/article/AA-00913 for a complete listing of
Security Vulnerabilities and versions affected.
If you'd like more information on ISC Subscription Support and
Advance Security Notifications, please visit
http://www.isc.org/support/.
Do you still have questions? Questions regarding this advisory should
go to security-offi...@isc.org. To report a new issue, please encrypt
your message using security-offi...@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
http://www.isc.org/downloads/ ).
ISC Security Vulnerability Disclosure Policy:
Details of our current security advisory policy and practice can be
found here: https://kb.isc.org/article/AA-00861
This Knowledge Base article https://kb.isc.org/article/AA-01495 is the
complete and official security advisory document.
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(C) 2017 Internet Systems Consortium
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