The msLoadQuery function in mapserv in MapServer 4.x before 4.10.4 and 5.x before 5.2.2 allows remote attackers to determine the existence of arbitrary files via a full pathname in the queryfile parameter, which triggers different error messages depending on whether this pathname exists.

More... (http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2009-0843)