CVE-2025-1971

Executive Summary

CVE-2025-1971 is a critical PHP Object Injection vulnerability discovered in the WordPress plugin "Export and Import Users and Customers" by Webtoffee. The flaw exists in all versions up to and including 2.6.2. An authenticated attacker with Administrator-level privileges can inject a malicious PHP object via deserialization of untrusted input from the form_data parameter. While the vulnerable plugin itself does not contain a POP (Property Oriented Programming) chain, the presence of any other plugin or theme with a suitable POP chain on the same WordPress site could allow the attacker to delete arbitrary files, retrieve sensitive data, or execute arbitrary code. The CVSS score is 7.2 (High), and the EPSS score is 0.0%, indicating low exploitation likelihood at this time. No public proof-of-concept or patch details are available.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Administrators should monitor for updates from the vendor (Webtoffee) and ensure no other plugins or themes with known POP chains are installed. The risk is amplified in environments with many third-party plugins.

CVSS Breakdown & Threat Level

• CVSS Score: 7.2 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: High (Administrator)
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

The high privileges required reduce the immediate threat, but the potential for full system compromise via a POP chain makes this a serious concern for WordPress sites with extensive plugin ecosystems.

Deep Dive & Mechanics

The vulnerability resides in the form_data parameter, which is deserialized without proper sanitization. In PHP, unserialize() is called on user-supplied data, allowing an attacker to instantiate arbitrary PHP objects. The attack flow is:

1. Authentication: The attacker must have Administrator-level access to the WordPress admin panel.
2. Crafting Payload: The attacker crafts a serialized PHP object that, when deserialized, triggers a POP chain.
3. Injection: The payload is sent via the form_data parameter in a request to the plugin's import/export functionality.
4. Exploitation: If a POP chain exists in another plugin or theme (e.g., via __destruct, __wakeup, or __toString magic methods), the attacker can execute arbitrary code, delete files, or exfiltrate data.

The vulnerability is classified as CWE-502 (Deserialization of Untrusted Data). The absence of a POP chain in the vulnerable plugin itself limits the impact, but the risk is real in complex WordPress installations.

Vulnerable vs. Patched Code

No patched version is available. The vulnerable code likely resembles:

// Vulnerable code in export-import-users-customers.php
$form_data = isset($_POST['form_data']) ? $_POST['form_data'] : '';
$data = unserialize(stripslashes($form_data));

A secure implementation would use JSON instead of serialization or validate the input:

// Patched code (hypothetical)
$form_data = isset($_POST['form_data']) ? $_POST['form_data'] : '';
$data = json_decode(stripslashes($form_data), true);
if (json_last_error() !== JSON_ERROR_NONE) {
    // Handle error
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• WordPress site with plugin version <= 2.6.2
• Administrator credentials
• A POP chain gadget from another installed plugin/theme (e.g., a plugin with a __destruct method that deletes files)

Exploitation Steps:

1. Identify POP Chain: Find a class in another plugin with a useful magic method. For example, a class FileDeleter with __destruct that calls unlink($this->file).
2. Craft Payload: Create a serialized object of that class with controlled properties.
3. Send Request: Use a tool like curl or Burp Suite to send a POST request to the plugin's admin page.

# Example payload (hypothetical)
curl -X POST http://target/wp-admin/admin.php?page=users-customers-import-export \
  -d 'action=import&form_data=O:10:"FileDeleter":1:{s:4:"file";s:15:"/etc/passwd";}'

Note: No public exploit code is available. The above is a conceptual example.

Blue Team

Detection:

• Monitor for unusual unserialize() calls in PHP error logs.
• Look for POST requests to the plugin's admin page with suspicious form_data parameters containing serialized PHP objects (e.g., O:, a:, s: patterns).
• Use WAF rules to block serialized PHP objects in POST parameters.

Hunting:

• Search for installed plugins with known POP chains (e.g., wp-cli, wp-super-cache).
• Review PHP error logs for deserialization warnings.

Indicators of Compromise (IOCs)

• Network: POST requests to /wp-admin/admin.php?page=users-customers-import-export with form_data containing serialized PHP objects.
• File System: Unexpected files in /tmp/ or web root (e.g., shell.php).
• Logs: PHP warnings like unserialize(): Error at offset in error logs.
• Process: Unusual PHP processes executing system commands.

Detection Engineering

YARA Rule

rule CVE_2025_1971_WordPress_Plugin_Deserialization {
    meta:
        description = "Detects serialized PHP objects in form_data parameter for CVE-2025-1971"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-1971"
    strings:
        $serialized = /form_data=O:\d+:"/
    condition:
        $serialized
}

Sigma Rule

title: CVE-2025-1971 WordPress Plugin Deserialization Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects attempts to exploit PHP Object Injection in Export and Import Users and Customers plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'page=users-customers-import-export'
        cs-uri-query|contains: 'form_data='
        cs-uri-query|re: 'form_data=O:\d+:"'
    condition: selection
falsepositives:
    - Legitimate plugin functionality (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-1971 WordPress Plugin Deserialization Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin.php"; http_uri; content:"page=users-customers-import-export"; http_uri; pcre:"/form_data=O:\d+:\"/"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin if not essential.
2. Restrict Administrator access to trusted users only.
3. Remove any unused plugins/themes that may contain POP chains.

Long-term:

• Monitor the vendor's website for a patched version (>= 2.6.3).
• Implement a Web Application Firewall (WAF) rule to block serialized PHP objects.
• Use a security plugin like Wordfence to detect deserialization attacks.
• Regularly audit installed plugins for known vulnerabilities.

Workaround:

• If the plugin must remain active, modify the code to use json_decode() instead of unserialize() (requires developer access).

Valters IT
Securing Digital Frontiers