a auth0 auth3 "A"*512 (2b) stack smashing detected stack smashing detected Both failures are because of __stack_chk_fail@plt: 0x000000000040095d : e8 8e fd ff ff call 0x4006f0 <__stack_chk_fail@plt> and: 0x000000000040092c : e8 7f fd ff ff call 0x4006b0 <__stack_chk_fail@plt> Ret.addr (4b) stack smashing detected stack smashing detected Undoubtedly, this is due to something similar. b $ cat /proc/sys/kernel/randomize_va_space 2 So, yes, full randomisation. It helps, because we cannot find the right address anymore using objdump. c Yes, then also the standard library addresses are randomised. d $ objdump -p auth0 auth0: file format elf64-x86-64 Program Header: ... STACK off 0x0000000000000000 vaddr 0x0000000000000000 paddr 0x0000000000000000 align 2**4 filesz 0x0000000000000000 memsz 0x0000000000000000 flags rw- As you can see, it has only rw permissions, not x. This helps, because otherwise we could overwrite the stack with code, and overwrite the return address with a stack address to execute our own code. I don't see any advantage in this though, when stack protection is enabled (because then it is infeasible to overwrite the return address and pass the checks), but I might be wrong.