CWE-51: Path Equivalence: '/multiple//internal/slash'

What is Path Equivalence: '/multiple//internal/slash'?

• Overview: Path Equivalence ('/multiple//internal/slash') vulnerability occurs when a system accepts and processes file paths with multiple internal slashes without proper validation, potentially leading to ambiguous path resolutions that can be exploited.

• Exploitation Methods:

• Attackers can exploit this vulnerability by crafting file paths with multiple slashes to bypass security controls and access unauthorized directories or files.
• Common attack patterns include directory traversal and path manipulation to escape restricted directories or access sensitive files.

• Security Impact:

• Direct consequences include unauthorized access to sensitive files and directories, leading to data leaks or corruption.
• Potential cascading effects involve attackers gaining a foothold to perform further attacks, such as privilege escalation or lateral movement.
• Business impact includes loss of sensitive data, legal repercussions, and damage to reputation.

• Prevention Guidelines:

• Specific code-level fixes include normalizing paths by removing redundant slashes and validating paths against a whitelist or a set of expected patterns.
• Security best practices involve implementing strict input validation and sanitization for all file path inputs.
• Recommended tools and frameworks include using security libraries or frameworks that provide built-in path validation and normalization functions.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: Not specified

Vulnerable Code Example

const fs = require('fs');

function readFile(filePath) {
    // Vulnerable code: accepts path with multiple slashes without normalization
    // This can lead to ambiguous path resolutions and possibly unintended file access
    return fs.readFileSync(filePath, 'utf-8');
}

// Example call
console.log(readFile('/var/www//html/index.html'));

Explanation

In the vulnerable code example, the function readFile accepts a file path as an argument but does not normalize it. This can result in path equivalence issues where multiple slashes ('//') are interpreted differently by the file system, potentially leading to accessing unintended files.

How to fix Path Equivalence: '/multiple//internal/slash'?

In JavaScript, particularly in Node.js, the path module provides a method called path.normalize() that can be used to clean up a path by resolving redundant slashes and other anomalies. This ensures that the path is consistently interpreted, reducing the risk of accessing unintended files due to path ambiguities.

Fixed Code Example

const fs = require('fs');
const path = require('path');

function readFile(filePath) {
    // Fixed code: normalize the file path to remove redundant slashes
    const normalizedPath = path.normalize(filePath);

    // Now use the normalized path for file operations
    return fs.readFileSync(normalizedPath, 'utf-8');
}

// Example call
console.log(readFile('/var/www//html/index.html'));

Explanation

In the fixed code example, the readFile function now uses path.normalize() to process the input file path. This method resolves any redundant slashes and other anomalies, ensuring that the path is interpreted consistently and securely. By normalizing the path before using it in file operations, we mitigate the risk of path equivalence vulnerabilities that could lead to unintended file access.