CVE-2016-1284: A REQUIRE assertion failure in rdataset.c can be deliberately triggered in servers performing NXDOMAIN redirection
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.
Document version: 1.0
Posting date: 3 February 2016
Program impacted: BIND 9 Supported Preview Edition (sometimes called "BIND 9 Subscription Edition")
Versions affected: 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).
Workarounds: Servers which do not use "nxdomain-redirect" are not at risk. Only servers using this feature of BIND 9 Supported Preview Edition are affected.
Active exploits: 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
Related Documents: See our BIND 9 Security Vulnerability Matrix for a complete listing of Security Vulnerabilities and versions affected.
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