CWE-1330: Remanent Data Readable after Memory Erase

What is Remanent Data Readable after Memory Erase?

• Overview: Remanent Data Readable after Memory Erase refers to a situation where sensitive information remains accessible in memory even after an attempt to clear or erase it. This can happen due to incomplete memory wipe processes or the physical characteristics of memory hardware, leaving data vulnerable to unauthorized access.

• Exploitation Methods:

• Attackers can exploit this vulnerability by physically accessing hardware or using advanced forensics to recover data remnants.
• Common attack patterns include analyzing memory dumps, using cold boot attacks, or employing techniques to read residual electrical charges in memory cells.

• Security Impact:

• Direct consequences of successful exploitation include unauthorized access to confidential data, such as passwords, encryption keys, or personal information.
• Potential cascading effects involve further breaches as attackers gain access to more sensitive systems or data due to compromised credentials.
• Business impact includes data breaches, loss of customer trust, legal repercussions, and financial losses.

• Prevention Guidelines:

• Specific code-level fixes involve ensuring that memory is thoroughly overwritten with random data multiple times before being freed or reused.
• Security best practices include implementing secure coding techniques that prioritize data encryption and memory management.
• Recommended tools and frameworks include using hardware that supports secure erase commands, employing self-encrypting drives, and following guidelines from security frameworks like NIST or ISO/IEC standards for data protection.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Security Hardware, Not Technology-Specific

Vulnerable Code Example

Python Example

import os

def handle_sensitive_data():
    # Simulated sensitive data
    sensitive_info = "SecretPassword123"
    
    # Vulnerable: Simply setting the variable to None
    # This does not guarantee that the memory is cleared.
    sensitive_info = None

# This function is called in a critical part of the application
handle_sensitive_data()

Explanation:

• Issue: The code sets sensitive_info to None with the intention of clearing the data. However, this approach does not guarantee that the memory is actually cleared or overwritten, which means the data could potentially be recovered from memory remnants.
• Impact: Residual data might remain in memory, leading to potential data leaks if memory is accessed by unauthorized processes or through errors.

How to fix Remanent Data Readable after Memory Erase?

To fix this vulnerability, it is crucial to actively overwrite the memory of the data before releasing the reference. This ensures that the sensitive data cannot be recovered. Here are the steps to properly fix this issue:

1. Explicitly overwrite sensitive data: Before setting the variable to None, overwrite its contents with non-sensitive data. This reduces the risk of recovery.
2. Use secure memory handling libraries if available: Some languages or environments provide libraries specifically designed for secure memory management.
3. Avoid storing sensitive data in memory longer than necessary: Only keep data in memory for the shortest time possible.

Fixed Code Example

import os

def handle_sensitive_data():
    # Simulated sensitive data
    sensitive_info = "SecretPassword123"
    
    # Securely overwrite the memory with non-sensitive data before releasing it
    sensitive_info = "x" * len(sensitive_info)  # Overwrite with non-sensitive data
    sensitive_info = None  # Now safely release the variable

# This function is called in a critical part of the application
handle_sensitive_data()

Explanation:

• Fix: The sensitive data is overwritten with a string of "x" characters before setting it to None. This ensures that the original data is not recoverable from memory.
• Security Principle: By overwriting the memory, we ensure no remanent data is left behind, adhering to best practices for secure data handling in memory. This approach significantly reduces the risk of sensitive data being accessed after its intended use.