Wrong byte!

ringzer0ctf

Task: 64-bit ELF that builds a shellcode buffer on the stack and executes it via call rax; the shellcode is a jmp/call/pop XOR-decoder with a corrupted key. Solution: reconstruct the shellcode from stack movs, recognize the single-byte XOR decoder, and use the known FLAG- prefix to recover the correct key (0x4a, not the embedded 0x13).