The DNS forwarder in Cisco IOS 12.0 through 12.4 and 15.0 through 15.6 and IOS XE 3.1 through 3.15 allows remote attackers to obtain sensitive information from process memory or cause a denial of service (data corruption or device reload) via a crafted DNS response, aka Bug ID CSCup90532.
https://ics-cert.us-cert.gov/advisories/ICSA-16-287-04
http://www.securitytracker.com/id/1036914
http://www.securityfocus.com/bid/93201
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160928-dns