CWE-244: Improper Clearing of Heap Memory Before Release ('Heap Inspection')

What is Improper Clearing of Heap Memory Before Release ('Heap Inspection')?

• Overview: Improper Clearing of Heap Memory Before Release, known as CWE-244, is a vulnerability that occurs when sensitive data such as passwords or encryption keys are not properly removed from memory after use. This often happens when using functions like realloc() that resize memory buffers. The original data can remain in memory, potentially exposing sensitive information to attackers.

• Exploitation Methods:

• Attackers can exploit this vulnerability through heap inspection attacks, which involve accessing memory dumps to retrieve sensitive data that was not cleared.
• Common attack patterns include using debugging tools or direct memory access techniques to capture and analyze memory remnants that may contain un-cleared sensitive information.

• Security Impact:

• Direct consequences include unauthorized access to sensitive information such as passwords, cryptographic keys, and personal data.
• Potential cascading effects could involve further exploitation of the system or network if sensitive credentials are compromised.
• Business impact may include data breaches, loss of customer trust, legal repercussions, and financial losses.

• Prevention Guidelines:

• Specific code-level fixes include explicitly clearing memory buffers containing sensitive data before releasing or reallocating them, such as using memset() to overwrite data.
• Security best practices suggest minimizing the use of realloc() for buffers holding sensitive information and ensuring sensitive data is cleared immediately after use.
• Recommended tools and frameworks include secure memory management libraries designed to handle sensitive data safely and tools that automate code analysis to detect improper memory handling.

Corgea can automatically detect and fix Improper Clearing of Heap Memory Before Release ('Heap Inspection') in your codebase. [Try Corgea free today](https://corgea.app).

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>
#include <string.h>

int main() {
    // Allocate memory for storing sensitive data (e.g., password)
    char *password = (char *)malloc(20 * sizeof(char));
    if (password == NULL) {
        perror("Failed to allocate memory");
        return 1;
    }
    strcpy(password, "SuperSecretPassword");

    // Code that uses the password...

    // Improper use of realloc without clearing the sensitive data
    password = realloc(password, 40 * sizeof(char)); // Memory reallocation without clearing
    if (password == NULL) {
        perror("Failed to reallocate memory");
        return 1;
    }

    // More code that uses the password...

    free(password); // Memory is freed without clearing sensitive data
    return 0;
}

Explanation

In the above vulnerable code, sensitive data stored in heap memory is not cleared before reallocating or freeing the memory. This can lead to potential exposure of sensitive data if the memory is reused or inspected by other processes.

How to fix Improper Clearing of Heap Memory Before Release ('Heap Inspection')?

To fix this vulnerability, ensure that any sensitive information stored in heap memory is securely erased before reallocating or freeing the memory. This can be achieved by manually setting the memory to zero or using secure memory handling functions like explicit_bzero.

Fixed Code Example

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

int main() {
    // Allocate memory for storing sensitive data (e.g., password)
    char *password = (char *)malloc(20 * sizeof(char));
    if (password == NULL) {
        perror("Failed to allocate memory");
        return 1;
    }
    strcpy(password, "SuperSecretPassword");

    // Code that uses the password...

    // Securely clear sensitive data before reallocating
    memset(password, 0, 20 * sizeof(char)); // Clear original memory block

    // Now safely reallocate the memory
    password = realloc(password, 40 * sizeof(char));
    if (password == NULL) {
        perror("Failed to reallocate memory");
        return 1;
    }

    // More code that uses the password...

    // Securely clear sensitive data before freeing
    memset(password, 0, 40 * sizeof(char)); // Clear expanded memory block
    free(password);
    return 0;
}

Explanation

In the fixed code example, we ensure that sensitive data is cleared from memory using memset before reallocating and freeing the memory. This prevents potential data leaks and ensures that sensitive information is not left in memory for other processes to access. This approach is crucial when handling confidential data, such as passwords, encryption keys, or personal information.