This indicates a vulnerability in iMatix Xitami Web Server 2.5c2. This vulnerability is caused by a stack overflow during handling of an excessively long "If-Modified-Since:" field in the http header. It allows remote attackers to execute arbitrary code by sending an http request with a specific header.
Xitami version 2.5c2 and prior.
System compromise, remote code execution.
Currently we are not aware of any official fix for this issue.