This is a proof-of-concept exploit that is able to escape from Native Client’s x86-64 sandbox on machines that are susceptible to the DRAM “rowhammer” problem. It works by inducing a bit flip in read-only code so that the code is no longer safe, producing instruction sequences that wouldn’t pass NaCl’s x86-64 validator. Note that this uses the CLFLUSH instruction, so it doesn’t work in newer versions of NaCl where this instruction is disallowed by the validator.