When a Java application uses the Java Native Interface (JNI) to call code written in another programming language, it can expose the application to weaknesses in that code, even if those weaknesses cannot occur in Java.
Many safety features that programmers may take for granted do not apply for native code, so you must carefully review all such code for potential problems. The languages used to implement native code may be more susceptible to buffer overflows and other attacks. Native code is unprotected by the security features enforced by the runtime environment, such as strong typing and array bounds checking.

Primary

Implementation

Access Control
Bypass Protection Mechanism

Automated Static Analysis
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 searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
High

Implementation
Implement error handling around the JNI call.

Implementation
Refactoring
Do not use JNI calls if you don't trust the native library.

Implementation
Refactoring
Be reluctant to use JNI calls. A Java API equivalent may exist.

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:

class Echo {

public native void runEcho();static {

System.loadLibrary("echo");
}public static void main(String[] args) {

new Echo().runEcho();
}
}

#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].

Unsafe JNI

SEC08-J
Define wrappers around native methods

JNI01-J
Safely invoke standard APIs that perform tasks using the immediate caller's class loader instance (loadLibrary)

JNI00-J
Define wrappers around native methods
Imprecise

SFP3
Use of an improper API

Allowed
This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

7 Pernicious Kingdoms
2006-07-19
Draft 3
2006-07-19

Eric Dalci
Cigital
2008-07-01
updated Demonstrative_Example, Potential_Mitigations, Time_of_Introduction

CWE Content Team
MITRE
2008-09-08
updated Relationships, Other_Notes, References, Taxonomy_Mappings, Weakness_Ordinalities

CWE Content Team
MITRE
2008-11-24
updated Description, Other_Notes

CWE Content Team
MITRE
2009-10-29
updated Description, Other_Notes

CWE Content Team
MITRE
2011-03-29
updated Demonstrative_Examples

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences, Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2012-05-11
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2013-02-21
updated Potential_Mitigations

CWE Content Team
MITRE
2014-07-30
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2017-11-08
updated Causal_Nature, Potential_Mitigations, References

CWE Content Team
MITRE
2019-01-03
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2020-02-24
updated References, Relationships, Type

CWE Content Team
MITRE
2021-03-15
updated Description

CWE Content Team
MITRE
2023-04-27
updated Detection_Factors, Relationships

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2024-02-29
4.14
2024-02-29
updated Demonstrative_Examples

Unsafe JNI