title: An error handling certain queries using the nxdomain-redirect feature could cause a REQUIRE assertion failure in db.c
description: An error in handling certain queries can cause an assertion failure when a server is using the nxdomain-redirect feature to cover a zone for which it is also providing authoritative service. A vulnerable server could be intentionally stopped by an attacker if it was using a configuration that met the criteria for the vulnerability and if the attacker could cause it to accept a query that possessed the required attributes. Please note: This vulnerability affects the "nxdomain-redirect" feature, which is one of two methods of handling NXDOMAIN redirection, and is only available in certain versions of BIND. Redirection using zones of type "redirect" is not affected by this vulnerability. Affects BIND 9.9.8-S1 -> 9.9.8-S3, 9.9.9-S1 -> 9.9.9-S6, 9.11.0-9.11.0-P1.
problem types: Only servers which are performing NXDOMAIN redirection using the "nxdomain-redirect" function are potentially vulnerable and then only a subset of those servers.  In order to be affected a server must be using nxdomain-redirect AND must be redirecting NXDOMAIN responses for a zone for which the server also provides authoritative service -- therefore a purely recursive server is not at risk, either.  Successful exploitation of the vulnerability will cause named to stop execution after encountering a REQUIRE assertion failure in db.c, resulting in denial of service to clients.
affected:
{
product: BIND 9
vendor: ISC
versions:
status: affected, version: BIND 9 9.9.8-S1 -> 9.9.8-S3, 9.9.9-S1 -> 9.9.9-S6, 9.11.0-9.11.0-P1
}
metrics:
cvssV3_0: [
attackComplexity: LOW
attackVector: NETWORK
availabilityImpact: HIGH
baseScore: 7.5
baseSeverity: HIGH
confidentialityImpact: NONE
integrityImpact: NONE
privilegesRequired: NONE
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
version: 3.0
]
solutions: Upgrade to the patched release most closely related to your current version of BIND. These can be downloaded from http://www.isc.org/downloads.
BIND 9 version 9.11.0-P2
BIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers.
BIND 9.9.9-S7
workarounds: Either provide an ordinary (that is: not redirected) NXDOMAIN for non-existent resource records in zones for which authoritative data is served on the same server or use redirect zones instead of the nxdomain-redirect feature.