It was reported [1] that Nagios Core's history.cgi is vulnerable to a buffer overflow because it used sprintf on user-supplied data that was not restricted in size.
Due to various protections of the operating system (history.cgi is compiled with SSP, FORTIFYSOURCE is enabled, etc.) this is not believed to be exploitable and would result in a denial of service to the user sending the input to history.cgi.
This has been fixed in svn (r2547)[2].
[1] http://archives.neohapsis.com/archives/fulldisclosure/2012-12/0108.html [2] http://nagios.svn.sourceforge.net/viewvc/nagios?view=revision&revision=2547