CVE-2016-1284: A REQUIRE assertion failure in rdataset.c can be deliberately triggered in servers performing NXDOMAIN redirection

CVE: CVE-2016-1284

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

Severity: Medium

Exploitable: Remotely

Description:

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.

Impact:

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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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 https://www.isc.org/downloads/). 

ISC Security Vulnerability Disclosure Policy: Details of our current security advisory policy and practice can be found in the ISC Software Defect and Security Vulnerability Disclosure Policy.

This Knowledgebase article is the complete and official security advisory document.

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