Apply by doing:
        cd /usr/src
        patch -p0 < 006_ibcs2.patch
And then rebuild your kernel.

Index: sys/compat/ibcs2/ibcs2_exec.c
===================================================================
RCS file: /cvs/src/sys/compat/ibcs2/ibcs2_exec.c,v
retrieving revision 1.14.6.1
retrieving revision 1.14.6.2
diff -u -r1.14.6.1 -r1.14.6.2
--- sys/compat/ibcs2/ibcs2_exec.c	3 Nov 2003 23:23:50 -0000	1.14.6.1
+++ sys/compat/ibcs2/ibcs2_exec.c	17 Nov 2003 16:41:19 -0000	1.14.6.2
@@ -425,11 +425,14 @@
 		size_t resid;
 		struct coff_slhdr *slhdr;
 		char buf[128], *bufp;	/* FIXME */
-		int len = sh.s_size, path_index, entry_len;
+		unsigned int len = sh.s_size, path_index, entry_len;
 		
 		/* DPRINTF(("COFF shlib size %d offset %d\n",
 			 sh.s_size, sh.s_scnptr)); */
 
+		if (len > sizeof(buf))
+			return (ENOEXEC);
+
 		error = vn_rdwr(UIO_READ, epp->ep_vp, (caddr_t) buf,
 				len, sh.s_scnptr,
 				UIO_SYSSPACE, IO_NODELOCKED, p->p_ucred,
@@ -446,6 +449,9 @@
 
 			/* DPRINTF(("path_index: %d entry_len: %d name: %s\n",
 				 path_index, entry_len, slhdr->sl_name)); */
+
+			if (entry_len > len)
+				return (ENOEXEC);
 
 			error = coff_load_shlib(p, slhdr->sl_name, epp);
 			if (error)