Oracle has release the 3rd critical patch update for 2008 (CPU July 2008). Critical patch updates mostly contain fixes to security vulnerabilities plus it would have non-security fixes too. This critical patch update contains 45 new security fixes across all products which includes14 for Oracle database. Please review the following URL to see if the product you are using requires this patch or not.
Also refer to Metalink note id 579278.1 for Oracle database and Fusion middleware products.
The next critical patch update (CPU) would be coming in October 2008.