A set of pre-production kernel packages of Red Hat Enterprise Linux for IBM Power architecture can be booted by the grub in Secure Boot mode even though it shouldn't. These kernel builds don't have the secure boot lockdown patches applied to it and can bypass the secure boot validations, allowing the attacker to load another non-trusted code.
A flaw was found in the Linux kernel, where a set of pre-production kernel packages of Red Hat Enterprise Linux for IBM Power architecture were signed with Red Hat's production secure boot keys. This issue allows kernel versions targeted for testing to eventually boot in PowerPC environments with the Secure Boot feature enabled. An attacker needs high privilege to install the non-production kernel packages in the target machine and make it the default boot option on grub2.