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.)
CWE-595 Variante Incompleto
Comparison of Object References Instead of Object Contents
This vulnerability occurs when code incorrectly checks if two object references point to the same memory location, rather than comparing the actual data or values contained within the objects. This…
Definição
What is CWE-595?
This vulnerability occurs when code incorrectly checks if two object references point to the same memory location, rather than comparing the actual data or values contained within the objects. This mistake prevents the software from correctly identifying when two separate objects hold equivalent content.
In many programming languages, the default comparison operator (like `==` in Java or `is` in Python) checks for *reference equality*. This means it only returns true if both variables point to the exact same object in memory. To properly compare the internal state or data of two objects, you must use a method designed for *value equality*, such as `.equals()` in Java, `.equals()` or value comparators in C#, or overriding the `==` operator in languages that support it.
This is a common pitfall, especially with strings and collections. For instance, using `==` on two Java `String` objects with the same text will often fail because they are distinct objects in memory. Developers must be intentional about their comparison logic, choosing the correct method based on whether they need to verify object identity or object content, as using the wrong check leads to flawed program logic and unexpected behavior.
Impacto no mundo real
Real-world CVEs caused by CWE-595
Ainda não há referências CVE públicas associadas a este CWE no catálogo da MITRE.
Como os atacantes a exploram
Trajeto do atacante passo a passo
- 1
In the example below, two Java String objects are declared and initialized with the same string values. An if statement is used to determine if the strings are equivalent.
- 2
However, the if statement will not be executed as the strings are compared using the "==" operator. For Java objects, such as String objects, the "==" operator compares object references, not object values. While the two String objects above contain the same string values, they refer to different object references, so the System.out.println statement will not be executed. To compare object values, the previous code could be modified to use the equals method:
- 3
In the following Java example, two BankAccount objects are compared in the isSameAccount method using the == operator.
- 4
Using the == operator to compare objects may produce incorrect or deceptive results by comparing object references rather than values. The equals() method should be used to ensure correct results or objects should contain a member variable that uniquely identifies the object.
- 5
The following example shows the use of the equals() method to compare the BankAccount objects and the next example uses a class get method to retrieve the bank account number that uniquely identifies the BankAccount object to compare the objects.
Exemplo de código vulnerável
Vulnerable Java
In the example below, two Java String objects are declared and initialized with the same string values. An if statement is used to determine if the strings are equivalent.
String str1 = new String("Hello");
String str2 = new String("Hello");
if (str1 == str2) {
System.out.println("str1 == str2");
} Exemplo de código seguro
Secure Java
However, the if statement will not be executed as the strings are compared using the "==" operator. For Java objects, such as String objects, the "==" operator compares object references, not object values. While the two String objects above contain the same string values, they refer to different object references, so the System.out.println statement will not be executed. To compare object values, the previous code could be modified to use the equals method:
if (str1.equals(str2)) {
System.out.println("str1 equals str2");
} What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Lista de verificação de prevenção
How to prevent CWE-595
- Implementation In Java, use the equals() method to compare objects instead of the == operator. If using ==, it is important for performance reasons that your objects are created by a static factory, not by a constructor.
Sinais de deteção
How to detect CWE-595
O Plexicus deteta automaticamente o CWE-595 e abre um PR de correção em menos de 60 segundos.
O Codex Remedium analisa cada commit, identifica esta fraqueza exata e entrega um pull request pronto para revisão com o patch. Sem tickets. Sem transferências.
Perguntas frequentes O que é o CWE-595?
Qual a gravidade do CWE-595?
Que linguagens ou plataformas são afetadas pelo CWE-595?
Como posso prevenir o CWE-595?
Como é que o Plexicus deteta e corrige o CWE-595?
Onde posso saber mais sobre o CWE-595?
Frequently asked questions
O que é o CWE-595?
This vulnerability occurs when code incorrectly checks if two object references point to the same memory location, rather than comparing the actual data or values contained within the objects. This mistake prevents the software from correctly identifying when two separate objects hold equivalent content.
Qual a gravidade do CWE-595?
A MITRE não publicou uma classificação de probabilidade de exploração para esta fraqueza. Trate-a como impacto médio até o seu modelo de ameaças provar o contrário.
Que linguagens ou plataformas são afetadas pelo CWE-595?
MITRE lists the following affected platforms: Java, JavaScript, PHP.
Como posso prevenir o CWE-595?
In Java, use the equals() method to compare objects instead of the == operator. If using ==, it is important for performance reasons that your objects are created by a static factory, not by a constructor.
Como é que o Plexicus deteta e corrige o CWE-595?
O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-595 em cada commit. Quando é encontrada uma correspondência, o nosso agente Codex Remedium abre um PR de correção com o código corrigido, testes e um resumo de uma linha para o revisor.
Onde posso saber mais sobre o CWE-595?
A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/595.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.
Fraquezas relacionadas
Weaknesses related to CWE-595
CWE-1025 Pai
Comparison Using Wrong Factors
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This vulnerability occurs when an application determines an object's trustworthiness or behavior solely by checking its class name. Since…
CWE-1097 Filho
Persistent Storable Data Element without Associated Comparison Control Element
This weakness occurs when a persistent data object lacks the necessary methods to be properly compared, which can lead to inconsistent or…
CWE-597 Filho
Use of Wrong Operator in String Comparison
This vulnerability occurs when a developer incorrectly compares string values, typically by using reference equality operators (like == or…
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