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.