CWE-762: Mismatched Memory Management Routines

What is Mismatched Memory Management Routines?

• Overview: Mismatched Memory Management Routines (CWE-762) occur when memory is allocated and deallocated using incompatible functions, leading to potential errors and vulnerabilities in software. For example, using malloc() to allocate memory and delete to deallocate it, or allocating on the stack and freeing it with free().

• Exploitation Methods:

• Attackers can exploit this vulnerability by causing memory leaks, buffer overflows, or memory corruption.
• Common attack patterns include triggering program crashes or executing arbitrary code by manipulating memory management errors.

• Security Impact:

• Direct consequences of successful exploitation include memory corruption, program crashes, and potential code execution.
• Potential cascading effects include further vulnerabilities being exposed and data integrity issues.
• Business impact involves loss of customer trust, potential data breaches, and financial losses due to downtime or remediation costs.

• Prevention Guidelines:

• Specific code-level fixes include ensuring that the same memory management routine pair is used for allocation and deallocation, such as malloc/free or new/delete.
• Security best practices involve rigorous code reviews, static code analysis, and adhering to consistent memory management policies.
• Recommended tools and frameworks include using automated tools like Valgrind or AddressSanitizer to detect mismatched memory management and employing smart pointers in C++ to manage memory automatically.

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Technical Details

Likelihood of Exploit: Low

Affected Languages: C, C++

Affected Technologies: Not specified

Vulnerable Code Example

Here's the improved content with corrections and enhancements to ensure clarity and adherence to best practices:

// Vulnerable code demonstrating mismatched memory management routines

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main() {
    // Allocating memory using malloc
    char *buffer = (char *)malloc(100 * sizeof(char)); // Line 9
    if (buffer == NULL) {
        fprintf(stderr, "Memory allocation failed\n");
        return 1;
    }

    strcpy(buffer, "This is a test string.");

    // Incorrectly deallocating memory using delete instead of free
    delete buffer; // Line 10: Mismatched memory management routine
    return 0;
}

Explanation:

• Issue: The code allocates memory using malloc but attempts to deallocate it using delete. This mismatched memory management routine can lead to undefined behavior, crashes, or memory leaks because malloc and delete are not compatible; malloc should always be paired with free.

How to fix Mismatched Memory Management Routines?

To fix the mismatched memory management routines, ensure that the deallocation function matches the allocation function used. In C, malloc() should be paired with free().

Best Practices:

1. Consistent Memory Management: Always pair malloc with free and new with delete. Mixing these can cause severe issues as they manage memory differently.
2. Error Checking: Always check the result of memory allocation functions like malloc to ensure they succeed before using the memory.
3. Code Review: Regularly review code to ensure proper use of memory management functions.

Fixed Code Example

// Fixed code with correct memory management routines

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main() {
    // Allocating memory using malloc
    char *buffer = (char *)malloc(100 * sizeof(char)); // Line 9
    if (buffer == NULL) {
        fprintf(stderr, "Memory allocation failed\n");
        return 1;
    }

    strcpy(buffer, "This is a test string.");

    // Correctly deallocating memory using free
    free(buffer); // Line 10: Properly matching free with malloc
    return 0;
}

Explanation:

• Fix: The code now correctly uses free(buffer); to deallocate the memory allocated with malloc. This ensures that the program manages memory safely and prevents undefined behavior.

By following these guidelines, you can prevent mismatched memory management issues in C programs, ensuring they run safely and efficiently.