https://bugs.gentoo.org/638434
Description: CVE-2017-10140: Reads DB_CONFIG from the current working directory
 Do not access DB_CONFIG when db_home is not set.
https://src.fedoraproject.org/rpms/libdb/raw/8047fa8580659fcae740c25e91b490539b8453eb/f/db-5.3.28-cwd-db_config.patch
From: Petr Kubat <pkubat@redhat.com>

--- a/env/env_open.c	2017-06-26 10:32:11.011419981 +0200
+++ b/env/env_open.c	2017-06-26 10:32:46.893721233 +0200
@@ -473,7 +473,7 @@
 	env->db_mode = mode == 0 ? DB_MODE_660 : mode;
 
 	/* Read the DB_CONFIG file. */
-	if ((ret = __env_read_db_config(env)) != 0)
+	if (env->db_home != NULL && (ret = __env_read_db_config(env)) != 0)
 		return (ret);
 
 	/*