CWE-587: Assignment of a Fixed Address to a Pointer

What is Assignment of a Fixed Address to a Pointer?

• Overview: This vulnerability occurs when a software program assigns a pointer to a fixed memory address instead of using dynamic memory allocation or initialization with NULL or 0. This practice can lead to software that is not portable across different environments or platforms, as the address may not be valid or accessible everywhere.

• Exploitation Methods:

• Attackers can exploit this vulnerability by predicting or controlling the fixed memory address and manipulating the data at that location.
• Common attack patterns include buffer overflow attacks where known fixed addresses are targeted to execute arbitrary code.

• Security Impact:

• Direct consequences include potential unauthorized access to sensitive memory areas, leading to data leaks or corruption.
• Potential cascading effects involve system crashes or unpredictable behavior across different environments.
• Business impact can range from compromised data integrity to loss of customer trust and financial losses due to system downtimes or breaches.

• Prevention Guidelines:

• Specific code-level fixes include avoiding the use of hard-coded addresses and employing dynamic memory allocation techniques.
• Security best practices involve regular code reviews and adopting secure coding standards that discourage fixed address usage.
• Recommended tools and frameworks include static analysis tools that can detect this pattern and memory management libraries that abstract away direct memory address manipulations.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: C, C++, C#, Assembly

Affected Technologies: Not specified

Vulnerable Code Example

// Vulnerable code with detailed comments explaining the security issue

#include <stdio.h>

int main() {
    int *fixed_address_pointer = (int *)0xdeadbeef; // {8}
    // This line assigns a fixed memory address to a pointer, which is dangerous.
    // It can lead to undefined behavior, security vulnerabilities, and system instability.
    // The address 0xdeadbeef is often used as a placeholder and may not be valid for dereferencing.

    *fixed_address_pointer = 42; // {12}
    // Dereferencing and writing to a fixed address can lead to a crash or memory corruption,
    // as this address is likely outside the program's allocated memory space.
    
    printf("Value at fixed address: %d\n", *fixed_address_pointer);
    return 0;
}

How to fix Assignment of a Fixed Address to a Pointer?

Assigning a fixed address to a pointer is dangerous because it can lead to undefined behavior, as the address may be outside the program's memory space or reserved for other uses. This is a common source of security vulnerabilities, including buffer overflows and arbitrary code execution.

To fix this issue:

1. Always allocate memory dynamically using standard memory management functions like malloc(), calloc(), or realloc().
2. Ensure that pointers are initialized to NULL if they are not immediately assigned a valid memory block.
3. Never hard-code memory addresses in your code. This ensures portability and stability across different environments and architectures.

Fixed Code Example

// Fixed code with comments explaining the security controls implemented

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

int main() {
    int *dynamic_pointer = (int *)malloc(sizeof(int)); // {8}
    // Allocate memory dynamically. This ensures that the pointer points to a valid memory block.
    
    if (dynamic_pointer == NULL) {
        // Check if memory allocation was successful
        fprintf(stderr, "Memory allocation failed\n");
        return 1;
    }
    
    *dynamic_pointer = 42; // {12}
    // Safely dereference the pointer as it points to a valid, allocated block of memory.
    
    printf("Value at allocated address: %d\n", *dynamic_pointer);
    
    free(dynamic_pointer); // {13}
    // Free the allocated memory to prevent memory leaks.
    
    return 0;
}

In the fixed code example, we dynamically allocate memory for the pointer and ensure that the memory is properly freed after use to prevent memory leaks. This approach makes the program safe, portable, and stable.