Summary In this advisory we are disclosing a vmap/vmalloc use-after-free vulnerability within the Android ION allocator, that impacts most Android devices that utilize ION. The exploitability of the vulnerability depends on how the various kernel drivers use the allocated ION buffers, the version of the kernel and the vendor specific modifications to the ION subsystem. In the most serious cases the vulnerability can be used to corrupt vmallocated kernel buffers, including kernel stacks, to achieve kernel code execution and compromise the integrity of the kernel. The ION allocator went over multiple refactors throughout its evolution, yet the vulnerability persisted within the Android common and the Linux upstream kernel branches.