output: #fixed code
                                  public void doCreateSlave(StaplerRequest req, StaplerResponse rsp, @QueryParameter String name,
                                @QueryParameter String description, @QueryParameter int executors,
                                @QueryParameter String remoteFsRoot, @QueryParameter String labels,
                                @QueryParameter String secret, @QueryParameter Node.Mode mode,
                                @QueryParameter(fixEmpty = true) String hash,
                                @QueryParameter boolean deleteExistingClients) throws IOException {
          if (!getSwarmSecret().equals(secret)) {
              rsp.setStatus(SC_FORBIDDEN);
              return;
          }
  
          try {
              Jenkins jenkins = Jenkins.get();
  
              jenkins.checkPermission(SlaveComputer.CREATE);
  
              List<NodeProperty<Node>> nodeProperties = new ArrayList<>();
  
              String[] toolLocations = req.getParameterValues("toolLocation");
              if (!ArrayUtils.isEmpty(toolLocations)) {
                  List<ToolLocation> parsedToolLocations = parseToolLocations(toolLocations);
                  nodeProperties.add(new ToolLocationNodeProperty(parsedToolLocations));
              }
  
              String[] environmentVariables = req.getParameterValues("environmentVariable");
              if (!ArrayUtils.isEmpty(environmentVariables)) {
                  List<EnvironmentVariablesNodeProperty.Entry> parsedEnvironmentVariables =
                          parseEnvironmentVariables(environmentVariables);
                  nodeProperties.add(
                          new EnvironmentVariablesNodeProperty(parsedEnvironmentVariables));
              }
  
              if (hash == null && jenkins.getNode(name) != null && !deleteExistingClients) {
                  // this is a legacy client, they won't be able to pick up the new name, so throw them away
                  // perhaps they can find another master to connect to
                  rsp.setStatus(SC_CONFLICT);
                  rsp.setContentType("text/plain; UTF-8");
                  rsp.getWriter().printf(
                          "A slave called '%s' already exists and legacy clients do not support name disambiguation%n",
                          name);
                  return;
              }
              if (hash != null) {
                  // try to make the name unique. Swarm clients are often replicated VMs, and they may have the same name.
                  name = name + '-' + hash;
              }
              // check for existing connections
              {
                  Node n = jenkins.getNode(name);
                  if (n != null && !deleteExistingClients) {
                      Computer c = n.toComputer();
                      if (c != null && c.isOnline()) {
                          // this is an existing connection, we'll only cause issues
                          // if we trample over an online connection
                          rsp.setStatus(SC_CONFLICT);
                          rsp.setContentType("text/plain; UTF-8");
                          rsp.getWriter().printf("A slave called '%s' is already created and on-line%n", name);
                          return;
                      }
                  }
              }
  
              SwarmSlave slave =
                      new SwarmSlave(
                              name,
                              "Swarm slave from "
                                      + req.getRemoteHost()
                                      + ((description == null || description.isEmpty())
                                              ? ""
                                              : (": " + description)),
                              remoteFsRoot,
                              String.valueOf(executors),
                              mode,
                              "swarm " + Util.fixNull(labels),
                              nodeProperties);
  
              jenkins.addNode(slave);
              rsp.setContentType("text/plain; charset=iso-8859-1");
              Properties props = new Properties();
              props.put("name", name);
              ByteArrayOutputStream bos = new ByteArrayOutputStream();
              props.store(bos, "");
              byte[] response = bos.toByteArray();
              rsp.setContentLength(response.length);
              ServletOutputStream outputStream = rsp.getOutputStream();
              outputStream.write(response);
              outputStream.flush();
          } catch (FormException e) {
              e.printStackTrace();
          }
      }
input: #vulnerable code 
                                  public void doCreateSlave(StaplerRequest req, StaplerResponse rsp, @QueryParameter String name,
                                @QueryParameter String description, @QueryParameter int executors,
                                @QueryParameter String remoteFsRoot, @QueryParameter String labels,
                                @QueryParameter String secret, @QueryParameter Node.Mode mode,
                                @QueryParameter(fixEmpty = true) String hash,
                                @QueryParameter boolean deleteExistingClients) throws IOException {
          if (!getSwarmSecret().equals(secret)) {
              rsp.setStatus(SC_FORBIDDEN);
              return;
          }
  
          try {
              Jenkins jenkins = Jenkins.getInstance();
  
              jenkins.checkPermission(SlaveComputer.CREATE);
  
              List<NodeProperty<Node>> nodeProperties = new ArrayList<>();
  
              String[] toolLocations = req.getParameterValues("toolLocation");
              if (!ArrayUtils.isEmpty(toolLocations)) {
                  List<ToolLocation> parsedToolLocations = parseToolLocations(toolLocations);
                  nodeProperties.add(new ToolLocationNodeProperty(parsedToolLocations));
              }
  
              String[] environmentVariables = req.getParameterValues("environmentVariable");
              if (!ArrayUtils.isEmpty(environmentVariables)) {
                  List<EnvironmentVariablesNodeProperty.Entry> parsedEnvironmentVariables =
                          parseEnvironmentVariables(environmentVariables);
                  nodeProperties.add(
                          new EnvironmentVariablesNodeProperty(parsedEnvironmentVariables));
              }
  
              if (hash == null && jenkins.getNode(name) != null && !deleteExistingClients) {
                  // this is a legacy client, they won't be able to pick up the new name, so throw them away
                  // perhaps they can find another master to connect to
                  rsp.setStatus(SC_CONFLICT);
                  rsp.setContentType("text/plain; UTF-8");
                  rsp.getWriter().printf(
                          "A slave called '%s' already exists and legacy clients do not support name disambiguation%n",
                          name);
                  return;
              }
              if (hash != null) {
                  // try to make the name unique. Swarm clients are often replicated VMs, and they may have the same name.
                  name = name + '-' + hash;
              }
              // check for existing connections
              {
                  Node n = jenkins.getNode(name);
                  if (n != null && !deleteExistingClients) {
                      Computer c = n.toComputer();
                      if (c != null && c.isOnline()) {
                          // this is an existing connection, we'll only cause issues
                          // if we trample over an online connection
                          rsp.setStatus(SC_CONFLICT);
                          rsp.setContentType("text/plain; UTF-8");
                          rsp.getWriter().printf("A slave called '%s' is already created and on-line%n", name);
                          return;
                      }
                  }
              }
  
              SwarmSlave slave =
                      new SwarmSlave(
                              name,
                              "Swarm slave from "
                                      + req.getRemoteHost()
                                      + ((description == null || description.isEmpty())
                                              ? ""
                                              : (": " + description)),
                              remoteFsRoot,
                              String.valueOf(executors),
                              mode,
                              "swarm " + Util.fixNull(labels),
                              nodeProperties);
  
              jenkins.addNode(slave);
              rsp.setContentType("text/plain; charset=iso-8859-1");
              Properties props = new Properties();
              props.put("name", name);
              ByteArrayOutputStream bos = new ByteArrayOutputStream();
              props.store(bos, "");
              byte[] response = bos.toByteArray();
              rsp.setContentLength(response.length);
              ServletOutputStream outputStream = rsp.getOutputStream();
              outputStream.write(response);
              outputStream.flush();
          } catch (FormException e) {
              e.printStackTrace();
          }
      } 
                              #location 15 
                              #vulnerability type NULL_DEREFERENCE