CWE-1252: CPU Hardware Not Configured to Support Exclusivity of Write and Execute Operations

What is CPU Hardware Not Configured to Support Exclusivity of Write and Execute Operations?

• Overview: This vulnerability arises when the CPU is not set up to enforce exclusivity of write and execute operations on memory, allowing attackers to execute data from any part of memory.

• Exploitation Methods:

• Attackers can exploit this by injecting malicious code into writable memory areas and then executing it.
• Common techniques include code injection and buffer overflow exploits, where attackers write harmful code to memory and execute it.

• Security Impact:

• Direct consequences include unauthorized code execution, potentially leading to system compromise.
• Potential cascading effects involve privilege escalation and unauthorized access to sensitive data.
• Business impact could include data breaches, service downtime, and damage to reputation.

• Prevention Guidelines:

• Ensure CPUs are configured to support execution and write exclusivity using hardware features like MMU/MPU.
• Follow security best practices like using non-executable stacks and enforcing data execution prevention (DEP).
• Utilize tools and frameworks that prioritize memory protection and enforce strict access control policies.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Microcontroller Hardware, Processor Hardware

Vulnerable Code Example

// Vulnerable code that does not properly configure memory protection
let buffer = new ArrayBuffer(1024);

// This function writes data to the buffer and then executes it
function executeCode(data) {
    let view = new DataView(buffer);
    for (let i = 0; i < data.length; i++) {
        view.setUint8(i, data.charCodeAt(i));  // Writes data to the buffer
    }
    eval(data);  // Dangerous: Executes data from writable memory, allowing code injection
}

// Example use
executeCode("console.log('This should not be executable!');");

Explanation:

• The code snippet demonstrates a security vulnerability where data is written to a buffer and then executed using eval. This allows for the execution of arbitrary code if the data is controlled by an attacker. The memory is both writable and executable, violating the principle of Write XOR Execute (W^X).

How to fix CPU Hardware Not Configured to Support Exclusivity of Write and Execute Operations?

To address this vulnerability, follow these steps:

1. Avoid using eval: Refrain from executing strings as code to prevent code injection attacks.
2. Use safer alternatives: Implement function factories or predefined functions that do not require executing arbitrary strings.
3. Leverage memory protection features: Configure your environment to enforce non-executable memory pages, supported by modern operating systems and hardware.

Fixed Code Example

// Fixed code with proper handling of memory protection
let buffer = new ArrayBuffer(1024);

// This function securely processes data without executing it
function processData(data) {
    let view = new DataView(buffer);
    for (let i = 0; i < data.length; i++) {
        view.setUint8(i, data.charCodeAt(i));  // Safely writes data to the buffer
    }
    
    // Log the data instead of executing it
    console.log("Data processed safely:", data);  // Safe: No execution of writable data
}

// Example use
processData("console.log('This is safe and processed correctly!');");

Explanation:

• In the fixed code, eval is removed, and the function is renamed to processData to reflect its secure operation. The code now logs the data instead of executing it, preventing code injection.
• This adheres to the W^X principle, ensuring no executable code resides in writable memory, thereby enhancing security.
• Configuring the operating system to enforce non-executable memory pages (e.g., DEP/NX bit) is recommended to prevent similar vulnerabilities in the future.