CWE-825 Base Incompleto

Expired Pointer Dereference

This vulnerability occurs when a program tries to use a pointer that still points to a memory location that has already been freed or released.

Definição

What is CWE-825?

This vulnerability occurs when a program tries to use a pointer that still points to a memory location that has already been freed or released.
This issue, often called a 'use-after-free' scenario, happens when your code frees a block of memory but accidentally keeps a reference (pointer) to it. Later, when that same pointer is used to read or write data, the memory may have been reallocated for a completely different purpose within your application or system. This means you're now interacting with data you didn't intend to, leading to unpredictable behavior. The consequences depend entirely on what now occupies that memory region. You might crash the program (denial of service), read sensitive information that belongs elsewhere (information exposure), or, in the worst case, have attacker-controlled data executed as code. This makes expired pointer dereference a critical weakness that can serve as a gateway to severe security breaches.
Impacto no mundo real

Real-world CVEs caused by CWE-825

  • CVE-2008-5013

    access of expired memory address leads to arbitrary code execution

  • CVE-2010-3257

    stale pointer issue leads to denial of service and possibly other consequences

  • CVE-2008-0062

    Chain: a message having an unknown message type may cause a reference to uninitialized memory resulting in a null pointer dereference (CWE-476) or dangling pointer (CWE-825), possibly crashing the system or causing heap corruption.

  • CVE-2007-1211

    read of value at an offset into a structure after the offset is no longer valid

Como os atacantes a exploram

Trajeto do atacante passo a passo

  1. 1

    The following code shows a simple example of a use after free error:

  2. 2

    When an error occurs, the pointer is immediately freed. However, this pointer is later incorrectly used in the logError function.

  3. 3

    The following code shows a simple example of a double free error:

  4. 4

    Double free vulnerabilities have two common (and sometimes overlapping) causes:

  5. 5

    - Error conditions and other exceptional circumstances - Confusion over which part of the program is responsible for freeing the memory

Exemplo de código vulnerável

Vulnerable C

The following code shows a simple example of a use after free error:

Vulnerável C 
char* ptr = (char*)malloc (SIZE);
  if (err) {
  	abrt = 1;
  	free(ptr);
  }
  ...
  if (abrt) {
  	logError("operation aborted before commit", ptr);
  }
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-825

  • Architecture and Design Choose a language that provides automatic memory management.
  • Implementation When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Sinais de deteção

How to detect CWE-825

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-825 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.

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Perguntas frequentes

Frequently asked questions

O que é o CWE-825?

This vulnerability occurs when a program tries to use a pointer that still points to a memory location that has already been freed or released.

Qual a gravidade do CWE-825?

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-825?

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

Como posso prevenir o CWE-825?

Choose a language that provides automatic memory management. When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.

Como é que o Plexicus deteta e corrige o CWE-825?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-825 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-825?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/825.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

Weaknesses related to CWE-825

CWE-119 Pai

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.…

CWE-120 Irmão

Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

This vulnerability occurs when a program copies data from one memory location to another without first verifying that the source data will…

CWE-123 Irmão

Write-what-where Condition

A write-what-where condition occurs when an attacker can control both the data written and the exact memory location where it's written,…

CWE-125 Irmão

Out-of-bounds Read

An out-of-bounds read occurs when software accesses memory outside the boundaries of a buffer, array, or similar data structure, reading…

CWE-130 Irmão

Improper Handling of Length Parameter Inconsistency

This vulnerability occurs when a program reads a structured data packet or message but fails to properly validate that the declared length…

CWE-466 Irmão

Return of Pointer Value Outside of Expected Range

This vulnerability occurs when a function returns a memory pointer that points outside the expected buffer range, potentially exposing…

CWE-786 Irmão

Access of Memory Location Before Start of Buffer

This vulnerability occurs when software attempts to read from or write to a memory location positioned before the official start of a…

CWE-787 Irmão

Out-of-bounds Write

This vulnerability occurs when software incorrectly writes data outside the boundaries of its allocated memory buffer, either beyond the…

CWE-788 Irmão

Access of Memory Location After End of Buffer

This vulnerability occurs when software attempts to read from or write to a memory buffer using an index or pointer that points past the…

Recursos

Further reading

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