CVE-2018-5737: BIND 9.12's serve-stale implementation can cause an assertion failure in rbtdb.c or other undesirable behavior, even if serve-stale is not enabled.
mcnally at isc.org
Fri May 18 22:30:30 UTC 2018
Document Version: 2.0
Posting date: 18 May 2018
Program Impacted: BIND
Versions affected: 9.12.0, 9.12.1
A problem with the implementation of the new serve-stale feature
in BIND 9.12 can lead to an assertion failure in rbtdb.c, even
when stale-answer-enable is off. Additionally, problematic
interaction between the serve-stale feature and NSEC aggressive
negative caching can in some cases cause undesirable behavior
from named, such as a recursion loop or excessive logging.
Deliberate exploitation of this condition could cause operational
problems depending on the particular manifestation -- either
degradation or denial of service.
Servers running a vulnerable version of BIND (9.12.0, 9.12.1)
which permit recursion to clients and which have the max-stale-ttl
parameter set to a non-zero value are at risk.
CVSS Score: 5.9
CVSS Vector: CVSS:3.0/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:
Setting "max-stale-ttl 0;" in named.conf will prevent exploitation
of this vulnerability (but will effectively disable the serve-stale
Setting "stale-answer enable off;" is not sufficient to prevent
exploitation, max-stale-ttl needs to be set to zero.
No known active exploits.
The error which can be exploited in this vulnerability is present
in only two public release versions of BIND, 9.12.0 and 9.12.1.
If you are running an affected version then upgrade to BIND
ISC would like to thank Tony Finch of the University of Cambridge
for his assistance in discovering and analyzing this vulnerability.
Document Revision History:
1.0 Advance Notification, 09 May 2018
1.1 BIND 9.12.1-P1 was recalled before public announcement
due to defect, the advisory language was re-written to be
clearer about the exploit risk, and the public disclosure
date was adjusted because of the problem with 9.12.1-P1,
17 May 2018
2.0 Public Disclosure, 18 May 2018
See our BIND9 Security Vulnerability Matrix at
https://kb.isc.org/article/AA-00913 for a complete listing of
Security Vulnerabilities and versions affected.
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Advance Security Notifications, please visit http://www.isc.org/support/.
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ISC patches only currently supported versions. When possible we
indicate EOL versions affected. (For current information on
which versions are actively supported, please see
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-01606 is
the complete and official security advisory document.
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