CWE-378 Base Rascunho High likelihood

Creation of Temporary File With Insecure Permissions

This vulnerability occurs when a program creates a temporary file but sets its file permissions too loosely, allowing other users or processes on the system to read, modify, or delete the file.

Definição

What is CWE-378?

This vulnerability occurs when a program creates a temporary file but sets its file permissions too loosely, allowing other users or processes on the system to read, modify, or delete the file.
When a temporary file is created with insecure permissions (like world-readable or world-writable), it becomes an easy target for attackers on the same system. They can directly read sensitive data from the file, inject malicious content into it, or even delete it to cause a denial of service. This is especially dangerous because developers often assume temporary files are private and secure, leading them to store sensitive information like session tokens, passwords, or configuration data in them. To prevent this, always use secure APIs designed for temporary file creation that enforce strict permissions by default, such as `mkstemp` on Unix-like systems. If you must use a lower-level function, explicitly set restrictive file permissions immediately after creation. Additionally, consider using alternative, more secure storage methods like memory-based structures for highly sensitive data, and ensure proper file cleanup to reduce the attack window.
Impacto no mundo real

Real-world CVEs caused by CWE-378

  • CVE-2022-24823

    A network application framework uses the Java function createTempFile(), which will create a file that is readable by other local users of the system

Como os atacantes a exploram

Trajeto do atacante passo a passo

  1. 1

    In the following code examples a temporary file is created and written to. After using the temporary file, the file is closed and deleted from the file system.

  2. 2

    However, within this C/C++ code the method tmpfile() is used to create and open the temp file. The tmpfile() method works the same way as the fopen() method would with read/write permission, allowing attackers to read potentially sensitive information contained in the temp file or modify the contents of the file.

  3. 3

    Similarly, the createTempFile() method used in the Java code creates a temp file that may be readable and writable to all users.

  4. 4

    Additionally both methods used above place the file into a default directory. On UNIX systems the default directory is usually "/tmp" or "/var/tmp" and on Windows systems the default directory is usually "C:\\Windows\\Temp", which may be easily accessible to attackers, possibly enabling them to read and modify the contents of the temp file.

Exemplo de código vulnerável

Vulnerable C

In the following code examples a temporary file is created and written to. After using the temporary file, the file is closed and deleted from the file system.

Vulnerável C 
FILE *stream;
  if( (stream = tmpfile()) == NULL ) {
  		perror("Could not open new temporary file\n");
  		return (-1);
  }
```
// write data to tmp file* 
  ...
  // remove tmp file
  rmtmp();
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-378

  • Requirements Many contemporary languages have functions which properly handle this condition. Older C temp file functions are especially susceptible.
  • Implementation Ensure that you use proper file permissions. This can be achieved by using a safe temp file function. Temporary files should be writable and readable only by the process that owns the file.
  • Implementation Randomize temporary file names. This can also be achieved by using a safe temp-file function. This will ensure that temporary files will not be created in predictable places.
Sinais de deteção

How to detect CWE-378

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-378 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-378?

This vulnerability occurs when a program creates a temporary file but sets its file permissions too loosely, allowing other users or processes on the system to read, modify, or delete the file.

Qual a gravidade do CWE-378?

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-378?

A MITRE não especificou as plataformas afetadas por este CWE — pode aplicar-se à maioria das stacks de aplicações.

Como posso prevenir o CWE-378?

Many contemporary languages have functions which properly handle this condition. Older C temp file functions are especially susceptible. Ensure that you use proper file permissions. This can be achieved by using a safe temp file function. Temporary files should be writable and readable only by the process that owns the file.

Como é que o Plexicus deteta e corrige o CWE-378?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-378 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-378?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/378.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

Weaknesses related to CWE-378

CWE-377 Pai

Insecure Temporary File

This vulnerability occurs when an application creates temporary files with insecure permissions or in predictable locations, allowing…

CWE-379 Irmão

Creation of Temporary File in Directory with Insecure Permissions

This vulnerability occurs when an application creates a temporary file in a directory that is too permissive, allowing unauthorized users…

Recursos

Further reading

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