CWE-695: Use of Low-Level Functionality

The following code defines a class named Echo. The class declares one native method (defined below), which uses C to echo commands entered on the console back to the user. The following C code defines the native method implemented in the Echo class:

Because the example is implemented in Java, it may appear that it is immune to memory issues like buffer overflow vulnerabilities. Although Java does do a good job of making memory operations safe, this protection does not extend to vulnerabilities occurring in source code written in other languages that are accessed using the Java Native Interface. Despite the memory protections offered in Java, the C code in this example is vulnerable to a buffer overflow because it makes use of gets(), which does not check the length of its input.

class Echo {                                                     public native void runEcho();static {                                                                 System.loadLibrary("echo");                            }public static void main(String[] args) {                                                                 new Echo().runEcho();                            }                      }

The following code defines a class named Echo. The class declares one native method (defined below), which uses C to echo commands entered on the console back to the user. The following C code defines the native method implemented in the Echo class:

Because the example is implemented in Java, it may appear that it is immune to memory issues like buffer overflow vulnerabilities. Although Java does do a good job of making memory operations safe, this protection does not extend to vulnerabilities occurring in source code written in other languages that are accessed using the Java Native Interface. Despite the memory protections offered in Java, the C code in this example is vulnerable to a buffer overflow because it makes use of gets(), which does not check the length of its input.

#include <jni.h>#include "Echo.h"//the java class above compiled with javah#include <stdio.h>                      JNIEXPORT void JNICALLJava_Echo_runEcho(JNIEnv *env, jobject obj){char buf[64];gets(buf);printf(buf);}

The following example opens a socket to connect to a remote server.

A Socket object is created directly within the Java servlet, which is a dangerous way to manage remote connections.

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {                                                                                 // Perform servlet tasks.                            ...                                                        // Open a socket to a remote server (bad).                            Socket sock = null;                            try {                               sock = new Socket(remoteHostname, 3000);                                                                    // Do something with the socket.                                  ...                            } catch (Exception e) {...}                      }