CWE-483: Incorrect Block Delimitation

What is Incorrect Block Delimitation?

• Overview: Incorrect Block Delimitation (CWE-483) occurs when code does not explicitly use delimiters like braces to define a block intended for multiple statements, leading to potential logic errors. This is common in languages like C and C++ where braces are optional.

• Exploitation Methods:

• Attackers can exploit this vulnerability by predicting or manipulating code paths to cause unintended execution flows.
• Common attack patterns include inserting additional statements or code that executes outside the intended block, potentially bypassing security checks.

• Security Impact:

• Direct consequences include incorrect program logic, leading to unauthorized actions or incorrect data processing.
• Potential cascading effects involve security checks being bypassed, leading to broader vulnerabilities within the application.
• Business impact can include data breaches, unauthorized access, and loss of customer trust.

• Prevention Guidelines:

• Specific code-level fixes involve always using braces for blocks, even if they contain a single statement.
• Security best practices include conducting thorough code reviews to ensure consistent use of block delimiters and adherence to coding standards.
• Recommended tools and frameworks include static analysis tools that can detect missing or inconsistent use of block delimiters.

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Technical Details

Likelihood of Exploit: Low

Affected Languages: C, C++

Affected Technologies: Not specified

Vulnerable Code Example

// Example of CWE-483: Incorrect Block Delimitation
#include <stdio.h>

void process_input(int value) {
    // Incorrect block delimitation due to missing braces
    if (value > 0)
        printf("Value is positive.\n");
        printf("Processing value...\n"); // This line will always execute, regardless of the condition
}

int main() {
    process_input(-1); // Expect no output, but will print "Processing value..."
    return 0;
}

Explanation

In the vulnerable code example, the if statement lacks braces {} to properly delimit the block of statements that should only execute when the condition is true. As a result, the line printf("Processing value...\n"); executes unconditionally, which is likely unintended behavior.

How to fix Incorrect Block Delimitation?

Incorrect block delimitation occurs when statements intended to be part of a single conditional block are not properly enclosed within braces {}. This often leads to logic errors where certain statements execute unconditionally, even though they are meant to be conditional. To fix this vulnerability:

1. Use Braces for All Conditional Blocks: Always enclose blocks of code in braces, even if they contain a single line. This reduces the risk of errors when additional lines are added later.
2. Consistent Formatting: Maintain a consistent code formatting style to improve readability and reduce the chance of incorrect logic.

Fixed Code Example

// Fixed version with correct block delimitation
#include <stdio.h>

void process_input(int value) {
    // Correct block delimitation with braces
    if (value > 0) {
        printf("Value is positive.\n");
        printf("Processing value...\n"); // Now only executes when condition is true
    }
}

int main() {
    process_input(-1); // No output, as expected
    return 0;
}

Explanation

In the fixed code example, the if statement is properly enclosed with braces {} to ensure that both printf statements execute only when the condition value > 0 is true. This corrects the logic error and prevents unintended behavior. Using braces consistently helps prevent similar issues in the future, especially when modifying or extending the code.