--- a/sys/vfs/nfs/krpc_subr.c
+++ b/sys/vfs/nfs/krpc_subr.c
@@ -473,6 +473,7 @@ xdr_string_encode(char *str, int len)
 	m = m_getl(mlen, M_WAITOK, MT_DATA, 0, NULL);
 	xs = mtod(m, struct xdr_string *);
 	m->m_len = mlen;
 	xs->len = txdr_unsigned(len);
 	bcopy(str, xs->data, len);
+	bzero(xs->data + len, dlen - len);	/* do not leak stale pad bytes */
 	return (m);
 }