CWE-415 Variante Rascunho High likelihood

Double Free

A double free vulnerability occurs when a program mistakenly calls the 'free()' function twice on the same block of memory.

Definição

What is CWE-415?

A double free vulnerability occurs when a program mistakenly calls the 'free()' function twice on the same block of memory.
This happens when a developer loses track of which pointers reference already-freed memory. The first free() call returns the memory to the system's pool for reuse, but the second call targets the same now-invalid address. This corrupts the memory manager's internal data structures, which can immediately crash the program or, more dangerously, create an opening for attackers to execute arbitrary code. Preventing double frees requires disciplined pointer management, such as setting pointers to NULL immediately after freeing them. While SAST tools can catch this pattern, Plexicus uses AI to suggest the actual code fix—like inserting that null assignment—saving hours of manual review and helping to secure your application's memory handling.
Vulnerability Diagram CWE-415
Double Free malloc p = 0x10A0 free(p) added to free-list free(p) again free-list corrupted Heap exploit arbitrary write The same chunk is freed twice → allocator metadata is poisoned.
Impacto no mundo real

Real-world CVEs caused by CWE-415

  • CVE-2006-5051

    Chain: Signal handler contains too much functionality (CWE-828), introducing a race condition (CWE-362) that leads to a double free (CWE-415).

  • CVE-2004-0642

    Double free resultant from certain error conditions.

  • CVE-2004-0772

    Double free resultant from certain error conditions.

  • CVE-2005-1689

    Double free resultant from certain error conditions.

  • CVE-2003-0545

    Double free from invalid ASN.1 encoding.

  • CVE-2003-1048

    Double free from malformed GIF.

  • CVE-2005-0891

    Double free from malformed GIF.

  • CVE-2002-0059

    Double free from malformed compressed data.

Como os atacantes a exploram

Trajeto do atacante passo a passo

  1. 1

    The following code shows a simple example of a double free vulnerability.

  2. 2

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

  3. 3

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

  4. 4

    Although some double free vulnerabilities are not much more complicated than this example, most are spread out across hundreds of lines of code or even different files. Programmers seem particularly susceptible to freeing global variables more than once.

  5. 5

    While contrived, this code should be exploitable on Linux distributions that do not ship with heap-chunk check summing turned on.

Exemplo de código vulnerável

Vulnerable C

The following code shows a simple example of a double free vulnerability.

Vulnerável C 
char* ptr = (char*)malloc (SIZE);
   ...
   if (abrt) { 
  	 free(ptr); 
   }
   ...
   free(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-415

  • Architecture and Design Choose a language that provides automatic memory management.
  • Implementation Ensure that each allocation is freed only once. After freeing a chunk, set the pointer to NULL to ensure the pointer cannot be freed again. In complicated error conditions, be sure that clean-up routines respect the state of allocation properly. If the language is object oriented, ensure that object destructors delete each chunk of memory only once.
  • Implementation Use a static analysis tool to find double free instances.
Sinais de deteção

How to detect CWE-415

Fuzzing High

Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.

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 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.)

Correção automática do Plexicus

O Plexicus deteta automaticamente o CWE-415 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-415?

A double free vulnerability occurs when a program mistakenly calls the 'free()' function twice on the same block of memory.

Qual a gravidade do CWE-415?

A MITRE classifica a probabilidade de exploração como Alta — esta fraqueza é ativamente explorada em campo e deve ser priorizada para remediação.

Que linguagens ou plataformas são afetadas pelo CWE-415?

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

Como posso prevenir o CWE-415?

Choose a language that provides automatic memory management. Ensure that each allocation is freed only once. After freeing a chunk, set the pointer to NULL to ensure the pointer cannot be freed again. In complicated error conditions, be sure that clean-up routines respect the state of allocation properly. If the language is object oriented, ensure that object destructors delete each chunk of memory only once.

Como é que o Plexicus deteta e corrige o CWE-415?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-415 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-415?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/415.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

Weaknesses related to CWE-415

CWE-825 Pai

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CWE-416 Irmão

Use After Free

Use After Free happens when a program continues to use a pointer to a memory location after that memory has been freed. This can lead to…

CWE-123 Par

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,…

Recursos

Further reading

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