Shim is the initial UEFI bootloader that handles chaining to a trusted fullbootloader under secure boot environments.A heap-based buffer overflow flaw was found the way shim parsed certainIPv6 addresses. If IPv6 network booting was enabled, a malicious servercould supply a crafted IPv6 address that would cause shim to crash or,potentially, execute arbitrary code. (CVE-2014-3676)An out-of-bounds memory write flaw was found in the way shim processedcertain Machine Owner Keys (MOKs). A local attacker could potentially usethis flaw to execute arbitrary code on the system. (CVE-2014-3677)An out-of-bounds memory read flaw was found in the way shim parsed certainIPv6 packets. A specially crafted DHCPv6 packet could possibly cause shimto crash, preventing the system from booting if IPv6 booting was enabled.(CVE-2014-3675)Red Hat would like to thank the SUSE Security Team for reporting theseissues.All shim users are advised to upgrade to these updated packages, whichcontain backported patches to correct these issues. The system must berebooted for this update to take effect.