#vulnerable code 
                                @Override
    public String getSystemSerialNumber() {
        if (this.cpuSerialNumber == null) {
            ArrayList<String> hwInfo = ExecutingCommand.runNative("system_profiler SPHardwareDataType");
            // Mavericks and later
            for (String checkLine : hwInfo) {
                if (checkLine.contains("Serial Number (system)")) {
                    String[] snSplit = checkLine.split("\\s+");
                    this.cpuSerialNumber = snSplit[snSplit.length - 1];
                    break;
                }
            }
            // Panther and later
            if (this.cpuSerialNumber == null) {
                for (String checkLine : hwInfo) {
                    if (checkLine.contains("r (system)")) {
                        String[] snSplit = checkLine.split("\\s+");
                        this.cpuSerialNumber = snSplit[snSplit.length - 1];
                        break;
                    }
                }
            }
            if (this.cpuSerialNumber == null) {
                this.cpuSerialNumber = "unknown";
            }
        }
        return this.cpuSerialNumber;
    } 
                            #location 6 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    public String getSystemSerialNumber() {
        if (this.cpuSerialNumber == null) {
            int service = 0;
            MachPort masterPort = new MachPort();
            int result = IOKit.INSTANCE.IOMasterPort(0, masterPort);
            if (result != 0) {
                LOG.error(String.format("Error: IOMasterPort() = %08x", result));
                this.cpuSerialNumber = "unknown";
            } else {
                service = IOKit.INSTANCE.IOServiceGetMatchingService(masterPort.getValue(),
                        IOKit.INSTANCE.IOServiceMatching("IOPlatformExpertDevice"));
                if (service == 0) {
                    this.cpuSerialNumber = "unknown";
                } else {
                    // Fetch the serial number
                    CFTypeRef serialNumberAsCFString = IOKit.INSTANCE.IORegistryEntryCreateCFProperty(service,
                            CFStringRef.toCFString("IOPlatformSerialNumber"),
                            CoreFoundation.INSTANCE.CFAllocatorGetDefault(), 0);
                    IOKit.INSTANCE.IOObjectRelease(service);
                    this.cpuSerialNumber = CfUtil.cfPointerToString(serialNumberAsCFString.getPointer());
                }
            }
        }
        return this.cpuSerialNumber;
    }