CWE-695: Use of Low-Level Functionality

Description

The product uses low-level functionality that is explicitly prohibited by the framework or specification under which the product is supposed to operate.

The use of low-level functionality can violate the specification in unexpected ways that effectively disable built-in protection mechanisms, introduce exploitable inconsistencies, or otherwise expose the functionality to attack.

Potential Impact

Other

Demonstrative Examples

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:

Bad

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

Bad

#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);}

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.

The Sun Java(TM) Tutorial provides the following description of JNI [See Reference]: The JNI framework lets your native method utilize Java objects in the same way that Java code uses these objects. A native method can create Java objects, including arrays and strings, and then inspect and use these objects to perform its tasks. A native method can also inspect and use objects created by Java application code. A native method can even update Java objects that it created or that were passed to it, and these updated objects are available to the Java application. Thus, both the native language side and the Java side of an application can create, update, and access Java objects and then share these objects between them.

The vulnerability in the example above could easily be detected through a source code audit of the native method implementation. This may not be practical or possible depending on the availability of the C source code and the way the project is built, but in many cases it may suffice. However, the ability to share objects between Java and native methods expands the potential risk to much more insidious cases where improper data handling in Java may lead to unexpected vulnerabilities in native code or unsafe operations in native code corrupt data structures in Java. Vulnerabilities in native code accessed through a Java application are typically exploited in the same manner as they are in applications written in the native language. The only challenge to such an attack is for the attacker to identify that the Java application uses native code to perform certain operations. This can be accomplished in a variety of ways, including identifying specific behaviors that are often implemented with native code or by exploiting a system information exposure in the Java application that reveals its use of JNI [See Reference].

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

Bad

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) {...}
                     }

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

Detection Methods

Automated Static Analysis High — Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then sea

Frequently Asked Questions

What is CWE-695?

CWE-695 (Use of Low-Level Functionality) is a software weakness identified by MITRE's Common Weakness Enumeration. It is classified as a Base-level weakness. The product uses low-level functionality that is explicitly prohibited by the framework or specification under which the product is supposed to operate.

How can CWE-695 be exploited?

Attackers can exploit CWE-695 (Use of Low-Level Functionality) to other. This weakness is typically introduced during the Implementation phase of software development.

How do I prevent CWE-695?

Follow secure coding practices, conduct code reviews, and use automated security testing tools (SAST/DAST) to detect this weakness early in the development lifecycle.

What is the severity of CWE-695?

CWE-695 is classified as a Base-level weakness (Medium abstraction). Its actual severity depends on the specific context and how the weakness manifests in your application.