Apply by doing:
       cd /usr/src
       patch -p0 < 029_httpd4.patch

And then rebuild and install httpd and its modules:
       cd usr.sbin/httpd
       make -f Makefile.bsd-wrapper obj
       make -f Makefile.bsd-wrapper cleandir
       make -f Makefile.bsd-wrapper depend
       make -f Makefile.bsd-wrapper
       make -f Makefile.bsd-wrapper install

If httpd had been started, you might want to run
       apachectl stop
before running "make install", and
       apachectl start
afterwards.

Index: usr.sbin/httpd/src/modules/standard/mod_rewrite.c
===================================================================
RCS file: /cvs/src/usr.sbin/httpd/src/modules/standard/mod_rewrite.c,v
retrieving revision 1.19.2.1
retrieving revision 1.19.2.2
diff -u -p -r1.19.2.1 -r1.19.2.2
--- usr.sbin/httpd/src/modules/standard/mod_rewrite.c   31 Oct 2003 00:20:31 -0000      1.19.2.1
+++ usr.sbin/httpd/src/modules/standard/mod_rewrite.c   9 Sep 2004 01:10:58 -0000       1.19.2.2
@@ -3080,16 +3080,17 @@ static char *lookup_map_dbmfile(request_
    datum dbmval;
    char *value = NULL;
    char buf[MAX_STRING_LEN];
+    size_t len;

    dbmkey.dptr  = key;
    dbmkey.dsize = strlen(key);
    if ((dbmfp = dbm_open(file, O_RDONLY, 0666)) != NULL) {
        dbmval = dbm_fetch(dbmfp, dbmkey);
        if (dbmval.dptr != NULL) {
-            memcpy(buf, dbmval.dptr,
-                   dbmval.dsize < sizeof(buf)-1 ?
-                   dbmval.dsize : sizeof(buf)-1  );
-            buf[dbmval.dsize] = '\0';
+            len = dbmval.dsize < sizeof(buf)-1 ?
+                  dbmval.dsize : sizeof(buf)-1;
+            memcpy(buf, dbmval.dptr, len);
+            buf[len] = '\0';
            value = ap_pstrdup(r->pool, buf);
        }
        dbm_close(dbmfp);