This ISC Security Advisory applies only to releases of the BIND 9 Supported Preview Edition, which is a special feature-development branch of BIND that is made available solely to subscription support customers (who are also notified directly concerning any security issues identified in this series). Releases in the Supported Preview Edition branch are denoted by an "-S" suffix and a sequence number, e.g. "BIND 9.9.8-S1"
Features which are created for BIND 9 Supported Preview Edition are ported to main-line open-source BIND releases after they have been refined in the Supported Preview Edition.
Posting date: 3 February 2016
Program Impacted: BIND
9 Supported Preview Edition (sometimes called "BIND
9 Subscription Edition")
9.9.8-S1 -> 9.9.8-S4
An error in handling flag values in incoming queries can be exploited to
deliberately trigger a REQUIRE assertion failure in rdataset.c on servers using the "nxdomain-redirect" option in BIND 9 Supported Preview Edition.
Servers configured for NXDOMAIN redirection using the "nxdomain-redirect" option are at risk from a constructed query with the right combination of attributes. Successful exploitation of this bug allows an attacker to cause a nameserver running BIND 9 Supported Preview Edition to stop execution after encountering a REQUIRE assertion failure in rdataset.c, resulting in denial of service to clients.
Servers configured for NXDOMAIN redirection using a "type redirect" zone rather than the "nxdomain-redirect" option are not at risk.
The assertion failure logged is:
rdataset.c:147: REQUIRE(((rdataset) != ((void *)0)) && ((const isc__magic_t *)(rdataset)->magic == (('D') << 24 | ('N') << 16 | ('S') << 8 | ('R'))))
The underlying bug is an assignment of a flag value to the wrong variable; this bug has existed in all Supported Preview releases since 9.9.6-S1, but it was harmless prior to the introduction of the "nxdomain-redirect" option.
CVSS Score: 5.4
CVSS Vector: (AV:N/AC:H/Au:N/C:N/I:N/A:C)
For more information on the Common Vulnerability Scoring System and to obtain your specific environmental score please visit: https://nvd.nist.gov/cvss.cfm?calculator&version=2&vector=(AV:N/AC:H/Au:N/C:N/I:N/A:C)
Servers which do not use "nxdomain-redirect" are not at risk. Only servers using this feature of BIND 9 Supported Preview Edition are affected.
No known active exploits.
Solution: Choose one of the following two options:
- A patch which will apply to BIND 9 Supported Preview Edition version 9.9.8-S4 is available upon request.
- A correction for the defect is included in BIND 9 Supported Preview Edition version 9.9.8-S5.
Document Revision History:
1.0 Advance Notification 27 January, 2016
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This Knowledge Base article https://kb.isc.org/article/AA-01348 is the complete and official security advisory document.
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