The kernel packages contain the Linux kernel, the core of any Linux operating system. This update fixes the following security issues: * A flaw was found in the way the Linux kernel"s Event Poll subsystem handled large, nested epoll structures. A local, unprivileged user could use this flaw to cause a denial of service. * A malicious Network File System version 4 server could return a crafted reply to a GETACL request, causing a denial of service on the client. Red Hat would like to thank Nelson Elhage for reporting CVE-2011-1083, and Andy Adamson for reporting CVE-2011-4131. This update also fixes several hundred bugs and adds enhancements. Refer to the Red Hat Enterprise Linux 6.3 Release Notes for information on the most significant of these changes, and the Technical Notes for further information, both linked to in the References. All Red Hat Enterprise Linux 6 users are advised to install these updated packages, which correct these issues, and fix the bugs and add the enhancements noted in the Red Hat Enterprise Linux 6.3 Release Notes and Technical Notes. The system must be rebooted for this update to take effect.