CWE-843 Base Incompleto

Access of Resource Using Incompatible Type ('Type Confusion')

Type confusion occurs when a program creates a resource—like a pointer, object, or variable—with one data type, but later incorrectly accesses it as a different, incompatible type.

Definição

What is CWE-843?

Type confusion occurs when a program creates a resource—like a pointer, object, or variable—with one data type, but later incorrectly accesses it as a different, incompatible type.
This mismatch can cause the program to misinterpret the data in memory, leading to logical errors, crashes, or unexpected behavior because the resource lacks the properties the code expects. In memory-unsafe languages like C and C++, this often results in dangerous out-of-bounds memory access, corrupting data or creating security vulnerabilities. While commonly seen with C/C++ unions when parsing complex data structures, type confusion can appear in many languages. For instance, PHP might fail if an array is passed where a single value is required, and languages like Perl that perform automatic type conversion can also introduce subtle bugs when variables are accessed as unintended types.
Impacto no mundo real

Real-world CVEs caused by CWE-843

  • CVE-2010-4577

    Type confusion in CSS sequence leads to out-of-bounds read.

  • CVE-2011-0611

    Size inconsistency allows code execution, first discovered when it was actively exploited in-the-wild.

  • CVE-2010-0258

    Improperly-parsed file containing records of different types leads to code execution when a memory location is interpreted as a different object than intended.

Como os atacantes a exploram

Trajeto do atacante passo a passo

  1. 1

    The following code uses a union to support the representation of different types of messages. It formats messages differently, depending on their type.

  2. 2

    The code intends to process the message as a NAME_TYPE, and sets the default message to "Hello World." However, since both buf.name and buf.nameID are part of the same union, they can act as aliases for the same memory location, depending on memory layout after compilation.

  3. 3

    As a result, modification of buf.nameID - an int - can effectively modify the pointer that is stored in buf.name - a string.

  4. 4

    Execution of the program might generate output such as:

  5. 5

    ``` Pointer of name is 10830 Pointer of name is now 10831 Message: ello World ```

Exemplo de código vulnerável

Vulnerable C

The following code uses a union to support the representation of different types of messages. It formats messages differently, depending on their type.

Vulnerável C 
#define NAME_TYPE 1
  #define ID_TYPE 2
  struct MessageBuffer
  {
  	int msgType;
  	union {
  		char *name;
  		int nameID;
  	};
  };
  int main (int argc, char **argv) {
  		struct MessageBuffer buf;
  		char *defaultMessage = "Hello World";
  		buf.msgType = NAME_TYPE;
  		buf.name = defaultMessage;
  		printf("Pointer of buf.name is %p\n", buf.name);
```
/* This particular value for nameID is used to make the code architecture-independent. If coming from untrusted input, it could be any value. */* 
  		
  		buf.nameID = (int)(defaultMessage + 1);
  		printf("Pointer of buf.name is now %p\n", buf.name);
  		if (buf.msgType == NAME_TYPE) {
  		```
  			printf("Message: %s\n", buf.name);
  		}
  		else {
  			printf("Message: Use ID %d\n", buf.nameID);
  		}
  }
Exemplo de código seguro

Secure pseudo

Seguro pseudo 
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
  const safe = validateAndEscape(input);
  return executeWithGuards(safe);
}
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-843

  • Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
  • Implementation Validate input at trust boundaries; use allowlists, not denylists.
  • Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
  • Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
  • Operation Monitor logs for the runtime signals listed in the next section.
Sinais de deteção

How to detect CWE-843

SAST High

Executar análise estática (SAST) na base de código à procura do padrão inseguro no fluxo de dados.

DAST Moderate

Executar testes dinâmicos de segurança de aplicações (DAST) contra o endpoint em execução.

Runtime Moderate

Monitorizar os registos em tempo de execução para traços de exceção invulgares, input malformado ou tentativas de contornar a autorização.

Code review Moderate

Revisão de código: sinalizar qualquer novo código que trate input desta superfície sem usar os ajudantes validados do framework.

Correção automática do Plexicus

O Plexicus deteta automaticamente o CWE-843 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.

Obter uma demonstração Experimente o Plexicus gratuitamente
Perguntas frequentes

Frequently asked questions

O que é o CWE-843?

Type confusion occurs when a program creates a resource—like a pointer, object, or variable—with one data type, but later incorrectly accesses it as a different, incompatible type.

Qual a gravidade do CWE-843?

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-843?

MITRE lists the following affected platforms: C, C++.

Como posso prevenir o CWE-843?

Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.

Como é que o Plexicus deteta e corrige o CWE-843?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-843 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-843?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/843.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

Weaknesses related to CWE-843

CWE-704 Pai

Incorrect Type Conversion or Cast

This vulnerability occurs when software incorrectly changes data from one type to another, leading to unexpected behavior or security flaws.

CWE-1389 Irmão

Incorrect Parsing of Numbers with Different Radices

This vulnerability occurs when software processes numeric input expecting standard decimal numbers (base 10), but fails to handle inputs…

CWE-588 Irmão

Attempt to Access Child of a Non-structure Pointer

This vulnerability occurs when code incorrectly treats a pointer to a basic data type (like an integer) as if it points to a structured…

CWE-681 Irmão

Incorrect Conversion between Numeric Types

This vulnerability occurs when a program converts a value from one numeric type to another (like a 64-bit integer to a 32-bit integer) and…

CWE-119 Pode preceder

Improper Restriction of Operations within the Bounds of a Memory Buffer

This vulnerability occurs when software accesses a memory buffer but reads from or writes to a location outside its allocated boundary.…

Recursos

Further reading

Pronto quando você estiver

Pare de pagar por desenvolvedor.
Comece a fechar o ciclo.

O Plexicus é o ASPM nativo de IA que verifica, filtra, corrige, pentesta e explica — de forma autónoma. Programadores ilimitados, repos ilimitados, ações de IA de utilização justa. Nível gratuito real, €269/mo anual quando estiver pronto.

Começar grátis Reservar uma demo