http://rdesktop.cvs.sourceforge.net/rdesktop/rdesktop/iso.c?r1=1.19&r2=1.20&view=patch&pathrev=HEAD
--- iso.c	2007/01/08 04:47:05	1.19
+++ iso.c	2008/02/14 11:45:13	1.20
@@ -98,6 +98,11 @@
 			next_be(s, length);
 		}
 	}
+	if (length < 4)
+	{
+		error("Bad packet header\n");
+		return NULL;
+	}
 	s = tcp_recv(s, length - 4);
 	if (s == NULL)
 		return NULL;