Multiple heap-based buffer underflows in the readPostBody function in cgiutil.c in mapserv in MapServer 4.x through 4.10.4 and 5.x before 5.4.2 allow remote attackers to execute arbitrary code via (1) a crafted Content-Length HTTP header or (2) a large HTTP request, related to an integer overflow that triggers a heap-based buffer overflow.  NOTE: this issue reportedly exists because of an incomplete fix for CVE-2009-0840.