CVE-2024-27561

Executive Summary

CVE-2024-27561 is a Server-Side Request Forgery (SSRF) vulnerability identified in WonderCMS version 3.1.3. The flaw resides in the installUpdateThemePluginAction function, where the installThemePlugin parameter is not properly sanitized. An attacker can inject a crafted URL into this parameter, forcing the application to make arbitrary HTTP requests from the server. This can lead to internal network reconnaissance, access to cloud metadata endpoints, or further exploitation of internal services. No official patch has been confirmed at the time of analysis.

Supply Chain & Package Security

WonderCMS is a flat-file PHP content management system distributed via GitHub and its official website. The vulnerability affects the core application logic, not a third-party package. Users should monitor the official WonderCMS repository for patch releases and consider manual code review or temporary mitigations.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, indicating insufficient data for a full vector. However, based on the SSRF nature, a reasonable estimate is:

• Attack Vector (AV): Network (N)
• Attack Complexity (AC): Low (L)
• Privileges Required (PR): None (N)
• User Interaction (UI): None (N)
• Scope (S): Unchanged (U)
• Confidentiality (C): High (H) – potential access to internal services
• Integrity (I): Low (L) – limited ability to modify internal data
• Availability (A): None (N)

Estimated CVSS v3.1 Score: 7.5 (High)

Threat Level: High – SSRF can lead to data exfiltration, internal scanning, and pivot attacks.

Deep Dive & Mechanics

The vulnerability exists in the installUpdateThemePluginAction function, which is responsible for installing or updating themes and plugins. The function accepts a URL via the installThemePlugin parameter and uses it to fetch a ZIP file from an external source. Due to insufficient validation, an attacker can supply a URL pointing to internal resources (e.g., http://169.254.169.254/latest/meta-data/ for AWS metadata) or other arbitrary endpoints.

Attack Flow:

1. The attacker sends a POST request to the vulnerable endpoint with a crafted installThemePlugin parameter.
2. The server makes an HTTP request to the attacker-controlled URL.
3. The response is processed, potentially exposing sensitive data or allowing further exploitation.

Root Cause: Lack of URL validation and restriction on allowed protocols or IP ranges.

Vulnerable vs. Patched Code

Vulnerable Code (WonderCMS 3.1.3):

function installUpdateThemePluginAction() {
    $url = $_POST['installThemePlugin'];
    // No validation of $url
    $zipContent = file_get_contents($url);
    // Process and extract zip
}

Patched Code (Hypothetical):

function installUpdateThemePluginAction() {
    $url = $_POST['installThemePlugin'];
    // Validate URL
    if (!filter_var($url, FILTER_VALIDATE_URL) || 
        !preg_match('/^https?:\/\/(?:[a-zA-Z0-9\-]+\.)+[a-zA-Z]{2,}/', $url)) {
        die('Invalid URL');
    }
    // Restrict to allowed domains
    $allowedHosts = ['github.com', 'wondercms.com'];
    $host = parse_url($url, PHP_URL_HOST);
    if (!in_array($host, $allowedHosts)) {
        die('Host not allowed');
    }
    $zipContent = file_get_contents($url);
    // Process and extract zip
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• WonderCMS 3.1.3 instance
• Attacker-controlled HTTP server to receive requests

Exploit Steps:

1. Identify the vulnerable endpoint (typically /installUpdateThemePluginAction).
2. Craft a POST request with installThemePlugin set to an internal URL, e.g., http://169.254.169.254/latest/meta-data/.
3. Observe the response for sensitive data.

Example cURL Command:

curl -X POST http://target-wondercms.com/installUpdateThemePluginAction \
  -d "installThemePlugin=http://169.254.169.254/latest/meta-data/"

Advanced Exploitation:

• Use SSRF to scan internal ports (e.g., http://192.168.1.1:8080/admin).
• Chain with other vulnerabilities for RCE.

Blue Team

Detection:

• Monitor outbound HTTP requests from the WonderCMS server to unexpected IPs.
• Log all installThemePlugin parameter values for anomalies.

Hunting:

• Search for requests containing internal IPs (e.g., 10., 172.16., 192.168., 169.254.).
• Alert on high volume of outbound connections from the web server.

Indicators of Compromise (IOCs)

• Network:
  • Outbound HTTP requests to internal IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 169.254.0.0/16)
  • Requests to cloud metadata endpoints (e.g., 169.254.169.254, 100.100.100.200)
• Logs:
  • POST requests to /installUpdateThemePluginAction with suspicious installThemePlugin values
• File System:
  • Unexpected files in the themes or plugins directories

Detection Engineering

YARA Rule

rule CVE_2024_27561_SSRF_WonderCMS {
    meta:
        description = "Detects SSRF attempts against WonderCMS CVE-2024-27561"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-27561"
    strings:
        $s1 = "installThemePlugin" ascii wide nocase
        $s2 = "169.254.169.254" ascii wide
        $s3 = "metadata" ascii wide
        $s4 = "internal" ascii wide
    condition:
        $s1 and ($s2 or $s3 or $s4)
}

Sigma Rule

title: WonderCMS SSRF Attempt (CVE-2024-27561)
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects SSRF attempts via installThemePlugin parameter
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        c-uri: '/installUpdateThemePluginAction'
        cs-uri-query|contains: 'installThemePlugin'
    filter:
        cs-uri-query|contains:
            - 'github.com'
            - 'wondercms.com'
    condition: selection and not filter
falsepositives:
    - Legitimate theme/plugin installations from allowed sources
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-27561 WonderCMS SSRF Attempt"; flow:to_server; content:"POST"; http_method; content:"/installUpdateThemePluginAction"; http_uri; content:"installThemePlugin"; http_client_body; pcre:"/installThemePlugin=(http:\/\/|https:\/\/)(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 installUpdateThemePluginAction functionality if not required.
2. Implement a web application firewall (WAF) rule to block requests with internal IPs in the installThemePlugin parameter.
3. Restrict outbound HTTP access from the WonderCMS server using network ACLs.

Long-term Fix:

• Apply official patch when released.
• Upgrade to a patched version of WonderCMS.
• Conduct code review to add URL validation and allowlisting.

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