CRLF injection vulnerability in the mail function in PHP 4.0.0 through 4.4.6 and 5.0.0 through 5.2.1 allows remote attackers to inject arbitrary e-mail headers and possibly conduct spam attacks via a control character immediately following folding of the (1) Subject or (2) To parameter, as demonstrated by a parameter containing a "\r\n\t\n" sequence, related to an increment bug in the SKIP_LONG_HEADER_SEP macro.