CWE-466: Return of Pointer Value Outside of Expected Range

What is Return of Pointer Value Outside of Expected Range?

• Overview: This vulnerability occurs when a function returns a pointer to memory that lies outside the bounds of the buffer it is supposed to reference, potentially leading to unexpected behavior or security issues.

• Exploitation Methods:

• Attackers can exploit this by manipulating the program to access unintended memory areas, leading to information disclosure or memory corruption.
• Common attack patterns include buffer overflow tactics and manipulating pointer arithmetic to access out-of-bounds memory.

• Security Impact:

• Direct consequences include unauthorized access to sensitive data and unexpected program behavior.
• Potential cascading effects can involve system crashes, data corruption, or providing a foothold for further exploitation.
• Business impact may include data breaches, loss of customer trust, and potential legal ramifications due to compromised data.

• Prevention Guidelines:

• Specific code-level fixes include thorough validation of pointer values and ensuring they point within the expected memory range.
• Security best practices involve using safer functions and avoiding unsafe pointer arithmetic.
• Recommended tools and frameworks include static analysis tools for detecting pointer-related vulnerabilities and adopting memory-safe programming practices.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: C, C++

Affected Technologies: Not specified

Vulnerable Code Example

C Example

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

// Function returning a pointer to an element in an array
int* getArrayElement(int* array, size_t size, int index) {
    // Vulnerability: No bounds checking, potentially returning a pointer outside the array
    return &array[index];
}

int main() {
    int numbers[] = {1, 2, 3, 4, 5};
    int* ptr = getArrayElement(numbers, 5, 10);  // Out-of-bounds access
    printf("Value: %d\n", *ptr);  // Undefined behavior
    return 0;
}

Explanation

In the vulnerable code example, the function getArrayElement returns a pointer to an element in the array without checking if the index is within the valid range. This can lead to undefined behavior if an out-of-bounds index is provided, as demonstrated in the main function when attempting to access numbers[10].

How to fix Return of Pointer Value Outside of Expected Range?

To fix this vulnerability, proper bounds checking should be performed before accessing the array. If the index is outside the valid range, the function should return NULL or handle the error appropriately. This ensures that the function does not return a pointer to memory outside the bounds of the provided array.

Fixed Code Example

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

// Safely get a pointer to an array element with bounds checking
int* getArrayElement(int* array, size_t size, int index) {
    // Check if index is within bounds of the array
    if (index < 0 || index >= size) {
        return NULL;  // Return NULL if index is out of bounds
    }
    return &array[index];  // Safe access
}

int main() {
    int numbers[] = {1, 2, 3, 4, 5};
    int* ptr = getArrayElement(numbers, 5, 10);
    if (ptr != NULL) {
        printf("Value: %d\n", *ptr);
    } else {
        printf("Error: Index out of bounds\n");  // Handle out-of-bounds access safely
    }
    return 0;
}

Explanation

In the fixed code example, we introduced bounds checking within the getArrayElement function. Before accessing the array, we verify whether the provided index is within the valid range (0 to size-1). If the index is out of bounds, the function returns NULL, indicating an error condition. This is then handled appropriately in the main function, preventing undefined behavior and mitigating the vulnerability.

Fixed Code Example