relay_header_pack(uint8_t *dest, const relay_header_t *src)
{
  set_uint8(dest, src->command);
  set_uint16(dest+1, htons(src->recognized));
  set_uint16(dest+3, htons(src->stream_id));
  memcpy(dest+5, src->integrity, 4);
  set_uint16(dest+9, htons(src->length));
}

The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.