The RFC 5011 implementation in rdata.c in ISC BIND 9.7.x and 9.8.x before 9.8.5-P2, 9.8.6b1, 9.9.x before 9.9.3-P2, and 9.9.4b1, and DNSco BIND 9.9.3-S1 before 9.9.3-S1-P1 and 9.9.4-S1b1, allows remote attackers to cause a denial of service (assertion failure and named daemon exit) via a query with a malformed RDATA section that is not properly handled during construction of a log message, as exploited in the wild in July 2013.