K19807532 : BIND vulnerability CVE-2020-8619

Security Advisory Description

The asterisk character (“*”) is allowed in DNS zone files, where it is most commonly present as a wildcard at a terminal node of the Domain Name System graph. However, the RFCs do not require and BIND does not enforce that an asterisk character be present only at a terminal node.

A problem can occur when an asterisk is present in an empty non-terminal location within the DNS graph. If such a node exists, after a series of queries, named can reach an inconsistent state that results in the failure of an assertion check in rbtdb.c, followed by the program exiting due to the assertion failure. (CVE-2020-8619)

Impact

You encounter this defect when you have both of the following conditions:

• A nameserver provides authoritative service for one or more zones.
• At least one zone contains an empty non-terminal entry containing an asterisk character.

A would-be attacker who is allowed to change zone content could, theoretically, introduce such a record in order to exploit this condition to cause denial-of-service (DoS); however, the use of this vector is unlikely because any such attack requires a significant privilege-level and is easily traceable.

BIND versions from 9.11.14 through 9.11.19 are impacted.