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. CVE: CVE-2018-5737 Document Version: 1.1 Posting date: 18 May 2018 Program Impacted: BIND Versions affected: 9.12.0, 9.12.1 Severity: Medium Exploitable: Remotely Description: 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. Impact: 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: 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: Setting "max-stale-ttl 0;" in named.conf will prevent exploitation of this vulnerability (but will effectively disable the serve-stale feature.) Setting "stale-answer enable off;" is not sufficient to prevent exploitation, max-stale-ttl needs to be set to zero. Active exploits: No known active exploits. Solution: 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 9.12.1-P2 Acknowledgements: 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 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.
CVE-2018-5736: Multiple transfers of a zone in quick succession can cause an assertion failure in rbtdb.c CVE: CVE-2018-5736 Document Version: 2.0 Posting date: 18 May 2018 Program Impacted: BIND Versions affected: 9.12.0 and 9.12.1 Severity: Medium Exploitable: Remotely, if an attacker can trigger a zone transfer Description: An error in zone database reference counting can lead to an assertion failure if a server which is running an affected version of BIND attempts several transfers of a slave zone in quick succession. This defect could be deliberately exercised by an attacker who is permitted to cause a vulnerable server to initiate zone transfers (for example: by sending valid NOTIFY messages), causing the named process to exit after failing the assertion test. Impact: Authoritative servers that serve slave zones are vulnerable to potential denial of service if all of the following are true: they are running an affected version of BIND (BIND 9.12.0 or 9.12.1) at least one of the zones for which they are providing service is of type "slave" they permit NOTIFY messages from any source. CVSS Score: 5.3 CVSS Vector: CVSS:3.0/AV:N/AC:H/PR:L/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:H/PR:L/UI:N/S:U/C:N/I:N/A:H Workarounds: For servers which must receive notifies to keep slave zone contents current, no complete workarounds are known although restricting BIND to only accept NOTIFY messages from authorized sources can greatly mitigate the risk of attack. Active exploits: No known active exploits. Solution: The reference counting 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 9.12.1-P1 Acknowledgements: ISC would like to thank SWITCH for informing us of this vulnerability. Document Revision History: 1.0 Advance Notification 09 May 2018 2.0 Public Disclosure 18 May 2018 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.
9.12.1 has just been replaced by 9.12.1_p2.
