app/aboot/aboot.c in the Qualcomm components in Android before 2016-07-05 on Nexus 5 and 7 (2013) devices does not validate the page size in the kernel header, which allows attackers to bypass intended access restrictions via a crafted boot image, aka Android internal bug 28820722 and Qualcomm internal bug CR684756.
https://source.codeaurora.org/quic/la/kernel/lk/commit/?id=2e21b3a57cac7fb876bcf43244d7cc3dc1f6030d