The setRequestHeader method of the XMLHttpRequest object in Microsoft Internet Explorer 5.01, 6, and 7 does not block dangerous HTTP request headers when certain 8-bit character sequences are appended to a header name, which allows remote attackers to (1) conduct HTTP request splitting and HTTP request smuggling attacks via an incorrect Content-Length header, (2) access arbitrary virtual hosts via a modified Host header, (3) bypass referrer restrictions via an incorrect Referer header, and (4) bypass the same-origin policy and obtain sensitive information via a crafted request header.

Microsoft XML Core Services (MSXML) 3.0 through 6.0 allows remote attackers to execute arbitrary code via the substringData method on a (1) TextNode or (2) XMLDOM object, which causes an integer overflow that leads to a buffer overflow.