A stack-based buffer overflow was found in libresolv when invoked from nssdns, allowing specially crafted DNS responses to seize control of EIP in the DNS client.

The buffer overflow occurs in the functions senddg (send datagram) and sendvc (send TCP) for the NSS module libnssdns.so.2 when calling getaddrinfo with AFUNSPEC family, or in some cases AFINET6 family. The use of AFUNSPEC (or AFINET6 in some cases) triggers the low-level resolver code to send out two parallel queries for A and AAAA. A mismanagement of the buffers used for those queries could result in the response of a query writing beyond the alloca allocated buffer created by resnquery.

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.