Isaimini.6 May 2026

if (callback != NULL) ((void (*)(void))callback)(); callback is a global 8‑byte variable at 0x00603010 , initialised to 0 . The only way to set it is through the ST instruction (store to memory).

FUN_00401000 entry point (main) FUN_00401200 parse_input FUN_00401430 execute FUN_00401780 op_add FUN_00401810 op_sub FUN_004018c0 op_load FUN_00401950 op_store FUN_00401b10 win int main(void) char buf[256]; read(0, buf, 256); parse_input(buf); execute(); puts("Failure!"); return 0; isaimini.6

payload=$(printf '\x01\x01\x10\x1b\x40\x00\x00\x00\x00\x00\x05\x10\x01\x09') # Make the binary executable chmod +x isaimini.6 if (callback

Thus, if we can , the program will call win after finishing the instruction stream, and we win. 5. Vulnerability Discovery The ST instruction performs: The interpreter keeps a register file :

parse_input tokenises the input and stores each instruction as a struct in a global array insts[128] . execute iterates over insts and dispatches to the appropriate handler based on the first byte (the opcode). The interpreter keeps a register file :