CVE-2025-31066

Executive Summary

CVE-2025-31066 is a Missing Authorization vulnerability in the WordPress plugin Acerola by Themeton, affecting versions from n/a through 1.6.5. This flaw allows an unauthenticated attacker to exploit incorrectly configured access control security levels, potentially leading to unauthorized data access or function execution. The vulnerability has a CVSS score of 5.3 (Medium), with a low EPSS score of 0.0% indicating low exploitation likelihood at this time. No public proof-of-concept or patch details are currently available.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Users are advised to monitor for updates from Themeton and apply patches as soon as they become available. The lack of a patch increases supply chain risk for sites using this plugin.

CVSS Breakdown & Threat Level

• CVSS Score: 5.3 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: Low
• Integrity Impact: None
• Availability Impact: None

The threat level is Medium due to the low complexity and no required privileges, but the impact is limited to confidentiality only.

Deep Dive & Mechanics

The vulnerability stems from missing authorization checks in the Acerola plugin's REST API endpoints or AJAX handlers. The plugin fails to verify user capabilities before executing sensitive operations, allowing unauthenticated attackers to access or modify data intended for authenticated users only. This is a classic CWE-862: Missing Authorization issue.

The affected functionality likely involves:

• Retrieving private or draft posts/pages
• Accessing user metadata or plugin settings
• Triggering administrative actions without proper nonce or capability checks

Vulnerable vs. Patched Code

Since no patch is available, a hypothetical vulnerable code example is provided:

Vulnerable Code (PHP):

add_action('wp_ajax_nopriv_acerola_get_data', 'acerola_get_data');
function acerola_get_data() {
    $data = get_option('acerola_private_data');
    wp_send_json_success($data);
}

Patched Code (Hypothetical):

add_action('wp_ajax_acerola_get_data', 'acerola_get_data');
add_action('wp_ajax_nopriv_acerola_get_data', 'acerola_get_data');
function acerola_get_data() {
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
    $data = get_option('acerola_private_data');
    wp_send_json_success($data);
}

The patch adds a capability check (current_user_can) and removes the nopriv action for privileged endpoints.

Exploitation & Lab Setup

Red Team

1. Reconnaissance: Identify WordPress sites using Acerola plugin via Shodan dorks or WPScan.
2. Exploitation: Send crafted HTTP requests to vulnerable endpoints:

   curl -X POST http://target.com/wp-admin/admin-ajax.php \
        -d "action=acerola_get_data"
   

3. Post-Exploitation: Extract sensitive data from the response.

Blue Team

1. Detection: Monitor for unusual AJAX requests to admin-ajax.php with action parameters related to Acerola.
2. Honeypot: Deploy a fake Acerola endpoint to capture attacker behavior.
3. Mitigation: Implement Web Application Firewall (WAF) rules to block unauthenticated access to plugin-specific actions.

Indicators of Compromise (IOCs)

• Network: HTTP POST requests to /wp-admin/admin-ajax.php with action=acerola_* parameters from unauthenticated sources.
• File: Presence of acerola directory under /wp-content/plugins/ with version <= 1.6.5.
• Log: WordPress debug logs showing wp_ajax_nopriv_acerola_* hooks being triggered.

Detection Engineering

YARA Rule

rule CVE_2025_31066_Acerola_Missing_Auth {
    meta:
        description = "Detects Acerola plugin files with missing authorization"
        author = "Valters IT"
        date = "2025-04-01"
        reference = "CVE-2025-31066"
    strings:
        $vuln_func = "wp_ajax_nopriv_acerola" nocase
        $cap_check = "current_user_can" nocase
    condition:
        $vuln_func and not $cap_check
}

Sigma Rule

title: CVE-2025-31066 - Acerola Missing Authorization Exploitation
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects exploitation attempts of missing authorization in Acerola plugin
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        c-uri: '/wp-admin/admin-ajax.php'
        cs-uri-query|contains: 'action=acerola_'
    condition: selection
falsepositives:
    - Legitimate admin actions
level: high

Suricata Rule

alert http any any -> any any (
    msg:"CVE-2025-31066 - Acerola Missing Authorization Attempt";
    flow:to_server;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=acerola_"; http_client_body;
    classtype:attempted-recon;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

1. Immediate: Disable the Acerola plugin until a patch is available.
2. Short-term: Implement a WAF rule to block unauthenticated requests to admin-ajax.php with action parameters starting with acerola_.
3. Long-term: Contact Themeton for a patched version. Consider replacing the plugin with an alternative that has active security support.
4. Monitoring: Enable detailed logging for AJAX requests and review logs for suspicious activity.

Valters IT - DevSecOps & Cyber Threat Intelligence