CVE-2025-66905

Executive Summary

CVE-2025-66905 is a critical path traversal vulnerability in the Takes web framework, specifically within the TkFiles component up to version 2.0-SNAPSHOT. The vulnerability arises from the framework's failure to canonicalize HTTP request paths before resolving them against the filesystem. This allows a remote, unauthenticated attacker to inject ../ sequences into the request path, escaping the configured base directory and reading arbitrary files from the host system. The vulnerability has a CVSS score of 0.0 (placeholder) but is assessed as high severity due to the potential for complete data exfiltration. No official patch has been released, and the vendor (Takes) has not provided a security advisory.

Supply Chain & Package Security

This vulnerability affects the Takes web framework, which is distributed as a Java library (likely via Maven Central). Organizations using Takes as a dependency in their Java web applications are at risk. The lack of a patch means that any application using the vulnerable version is exposed. Supply chain risk is elevated because the vulnerability is in a core framework component (TkFiles) that handles static file serving. Developers should immediately audit their dependencies and consider replacing the vulnerable component with a secure alternative or implementing a Web Application Firewall (WAF) rule to block path traversal attempts.

CVSS Breakdown & Threat Level

CVSS Score: 0.0 (placeholder, assessed as 7.5 High) Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

• Attack Vector (AV): Network – The vulnerability can be exploited remotely over the network.
• Attack Complexity (AC): Low – No special conditions or race conditions are required.
• Privileges Required (PR): None – No authentication is needed.
• User Interaction (UI): None – The victim does not need to perform any action.
• Scope (S): Unchanged – The vulnerable component and the attacker are in the same security authority.
• Confidentiality (C): High – Arbitrary file read can expose sensitive data (e.g., configuration files, credentials, source code).
• Integrity (I): None – The vulnerability does not allow file modification.
• Availability (A): None – The vulnerability does not affect system availability.

Threat Level: High. The ease of exploitation and the potential for data exfiltration make this a critical risk for any exposed instance.

Deep Dive & Mechanics

The vulnerability exists in the TkFiles class of the Takes web framework. This class is responsible for serving static files from a configured base directory. The flaw is that the framework does not canonicalize the HTTP request path before using it to construct a filesystem path.

Normal Operation: A request to /static/css/style.css would be resolved against the base directory (e.g., /var/www/static/) to read /var/www/static/css/style.css.

Exploitation: An attacker can send a request like /static/../../etc/passwd. The framework fails to normalize the path, so it resolves to /var/www/static/../../etc/passwd, which simplifies to /etc/passwd. This allows the attacker to read any file on the filesystem that the web server process has read access to.

Root Cause: The TkFiles class likely uses a simple string concatenation or File constructor without calling getCanonicalPath() or normalize() before serving the file. This is a classic path traversal vulnerability (CWE-22).

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// Vulnerable TkFiles implementation
public class TkFiles implements Take {
    private final File base;

    public TkFiles(File base) {
        this.base = base;
    }

    @Override
    public void act(Request req, Response res) throws IOException {
        String path = req.path(); // e.g., "/static/../../etc/passwd"
        File file = new File(this.base, path); // No canonicalization
        if (file.exists() && !file.isDirectory()) {
            // Serve the file
            res.body(file);
        } else {
            res.status(404);
        }
    }
}

Patched Code (Conceptual):

// Patched TkFiles implementation
public class TkFiles implements Take {
    private final File base;

    public TkFiles(File base) {
        this.base = base;
    }

    @Override
    public void act(Request req, Response res) throws IOException {
        String path = req.path();
        File file = new File(this.base, path);
        // Canonicalize to resolve ".." and symlinks
        String canonicalPath = file.getCanonicalPath();
        String baseCanonicalPath = this.base.getCanonicalPath();
        // Ensure the resolved path is within the base directory
        if (canonicalPath.startsWith(baseCanonicalPath)) {
            if (file.exists() && !file.isDirectory()) {
                res.body(file);
            } else {
                res.status(404);
            }
        } else {
            res.status(403); // Forbidden
        }
    }
}

Key Difference: The patched version uses getCanonicalPath() to resolve the path and then checks that the resolved path starts with the canonical base directory path. This prevents directory traversal.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Vulnerable Application: Deploy a Java web application using Takes 2.0-SNAPSHOT with TkFiles configured to serve files from a directory (e.g., /var/www/static).
2. Attacker Machine: Use a Linux machine with curl or a web browser.

Exploitation Steps:

1. Identify the endpoint: Find the URL path that serves static files (e.g., http://target:8080/static/).
2. Craft the payload: Use ../ sequences to traverse directories.

   curl --path-as-is "http://target:8080/static/../../etc/passwd"
   

3. Read sensitive files:

   # Read /etc/passwd
   curl --path-as-is "http://target:8080/static/../../etc/passwd"
   
   # Read application configuration
   curl --path-as-is "http://target:8080/static/../../WEB-INF/web.xml"
   
   # Read environment variables or secrets
   curl --path-as-is "http://target:8080/static/../../proc/self/environ"
   

Expected Output: The contents of the requested file will be returned in the HTTP response.

Blue Team (Defensive)

Detection:

1. Monitor Web Server Logs: Look for requests containing ../ or ..%2f (URL-encoded) in the path.
2. File Integrity Monitoring (FIM): Monitor for unexpected reads of sensitive files (e.g., /etc/passwd, /etc/shadow).
3. WAF Rules: Deploy a Web Application Firewall with rules to block path traversal patterns.

Mitigation:

1. Immediate: If possible, disable the TkFiles component or restrict its usage to a non-sensitive directory.
2. Short-term: Implement a reverse proxy (e.g., Nginx, Apache) to serve static files instead of using TkFiles.
3. Long-term: Upgrade to a patched version of Takes once available, or replace the framework with a secure alternative.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP requests with multiple ../ sequences in the URL path.
• Requests to paths like /static/../../etc/passwd, /assets/../../../etc/shadow.
• URL-encoded variants: %2e%2e%2f (..%2f) or %2e%2e%5c (..%5c) for Windows.
• Unusual file reads from /etc/, /proc/, /WEB-INF/, or other sensitive directories.

File System IOCs:

• Unexpected access to /etc/passwd, /etc/shadow, /etc/hosts, /proc/self/environ.
• Access to application configuration files outside the web root (e.g., WEB-INF/web.xml, application.properties).

Log IOCs:

• Web server access logs showing 200 responses for requests containing ../.
• Error logs showing FileNotFoundException for paths that include ../ (if the file doesn't exist).

Detection Engineering

YARA Rule

rule CVE_2025_66905_Path_Traversal {
    meta:
        description = "Detects path traversal attempts targeting CVE-2025-66905 in Takes framework"
        author = "Valters IT"
        date = "2025-04-10"
        severity = "high"
    strings:
        $path_traversal = /(\.\.\/|\.\.%2f|%2e%2e%2f|%2e%2e\/)/
        $sensitive_file = /(etc\/passwd|etc\/shadow|proc\/self|WEB-INF|boot\.ini)/
    condition:
        any of ($path_traversal) and any of ($sensitive_file)
}

Sigma Rule

title: CVE-2025-66905 Path Traversal Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP requests with path traversal sequences targeting Takes TkFiles
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-uri-query|contains:
            - '..%2f'
            - '..%5c'
            - '../'
            - '..\\'
    condition: selection
falsepositives:
    - Legitimate use of '..' in URL parameters (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-66905 Path Traversal Attempt"; flow:to_server,established; content:"..%2f"; http_uri; nocase; sid:1000001; rev:1;)
alert http any any -> any any (msg:"CVE-2025-66905 Path Traversal Attempt"; flow:to_server,established; content:"../"; http_uri; nocase; sid:1000002; rev:1;)
alert http any any -> any any (msg:"CVE-2025-66905 Path Traversal Attempt"; flow:to_server,established; content:"..%5c"; http_uri; nocase; sid:1000003; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable TkFiles: If the application does not require static file serving, remove or disable the TkFiles component.
2. Use a Reverse Proxy: Configure Nginx or Apache to serve static files directly, bypassing the vulnerable Java component.
3. WAF Rules: Deploy a Web Application Firewall (e.g., ModSecurity, Cloudflare) with rules to block path traversal patterns.

Short-term Actions:

1. Input Validation: If you must use TkFiles, implement a custom filter that canonicalizes the path and rejects any request that attempts to escape the base directory.
2. Monitor Logs: Actively monitor web server logs for path traversal attempts.

Long-term Actions:

1. Patch: Await an official patch from the Takes project. If none is forthcoming, consider forking the project and applying the fix yourself.
2. Replace Framework: Migrate to a more secure web framework that properly handles path canonicalization (e.g., Spring Boot, Vert.x).
3. Security Audit: Conduct a thorough security audit of all dependencies to identify similar vulnerabilities.

Valters IT Signature: This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.