CWE-1325: Improperly Controlled Sequential Memory Allocation

What is Improperly Controlled Sequential Memory Allocation?

• Overview: Improperly Controlled Sequential Memory Allocation is a vulnerability where software allocates memory for multiple objects separately without limiting the total memory used, potentially leading to excessive memory consumption.

• Exploitation Methods:

• Attackers can exploit this by creating numerous objects, each triggering separate memory allocations.
• Common attack patterns include flooding the application with requests to allocate objects until system resources are exhausted.

• Security Impact:

• Direct consequences include denial of service (DoS) due to resource exhaustion.
• Potential cascading effects might involve system instability or crashes.
• Business impact includes service downtime, customer dissatisfaction, and potential financial loss.

• Prevention Guidelines:

• Implement limits on the total memory usage for all allocated objects.
• Use memory pooling strategies to manage memory more efficiently.
• Employ monitoring and alerting systems to detect unusual memory usage patterns.
• Apply resource allocation quotas and use dynamic resource management tools.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: C, C++, Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

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

#define MAX_OBJECTS 100000

void allocate_objects(int num_objects) {
    int *objects[num_objects]; // Array to store pointers to allocated memory

    for (int i = 0; i < num_objects; i++) {
        objects[i] = (int *)malloc(sizeof(int) * 1024); // Allocate 1024 integers
        if (!objects[i]) {
            fprintf(stderr, "Memory allocation failed at object %d\n", i);
            exit(1);
        }
    }
    // No limit on num_objects, which can exhaust system memory
}

int main() {
    allocate_objects(200000); // Attempt to allocate more objects than reasonable
    return 0;
}

Explanation:

• The code attempts to allocate memory for a large number of objects without verifying if the number of objects surpasses a reasonable limit.
• The absence of a limit on num_objects can lead to system memory exhaustion, demonstrating improperly controlled sequential memory allocation.

How to fix Improperly Controlled Sequential Memory Allocation?

To address this vulnerability, it's crucial to:

1. Set a Limit: Enforce a maximum limit on the number of objects that can be allocated.
2. Monitor Memory Usage: Track allocated memory and ensure it does not exceed a predefined safe threshold.
3. Graceful Handling: Manage situations where the allocation limit is reached by logging errors or providing alternatives.

Fixed Code Example

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

#define MAX_OBJECTS 100000

void allocate_objects(int num_objects) {
    if (num_objects > MAX_OBJECTS) { // Check against maximum limit
        fprintf(stderr, "Request exceeds maximum object limit of %d\n", MAX_OBJECTS);
        return;
    }

    int *objects[num_objects];
    for (int i = 0; i < num_objects; i++) {
        objects[i] = (int *)malloc(sizeof(int) * 1024);
        if (!objects[i]) {
            fprintf(stderr, "Memory allocation failed at object %d\n", i);
            // Free previously allocated memory
            for (int j = 0; j < i; j++) {
                free(objects[j]);
            }
            exit(1);
        }
    }

    // Free allocated memory after use to prevent memory leaks
    for (int i = 0; i < num_objects; i++) {
        free(objects[i]);
    }
}

int main() {
    allocate_objects(50000); // Within the reasonable limit
    return 0;
}

Explanation:

• Limit Check: Before allocating, the function checks if num_objects exceeds MAX_OBJECTS, preventing excessive allocation.
• Cleaning Up: If memory allocation fails, previously allocated memory is freed to prevent leaks.
• Freeing Memory: All allocated memory is freed after use to prevent memory leaks.
• Reasonable Limits: The main function now attempts to allocate a reasonable number of objects, demonstrating how to keep within safe limits.