CVE-2026-2599: WordPress Database Plugin Object Injection

CVE-2026-2599 Overview

The Database for Contact Form 7, WPforms, Elementor forms plugin for WordPress contains a critical PHP Object Injection vulnerability in all versions up to and including 1.4.7. The vulnerability exists in the download_csv function, which deserializes untrusted input without proper validation. This flaw enables unauthenticated attackers to inject malicious PHP objects into the application.

While no known Property-Oriented Programming (POP) chain exists within the vulnerable plugin itself, the exploitation risk increases significantly when combined with other WordPress plugins or themes that contain POP chains. Successful exploitation could lead to arbitrary file deletion, sensitive data retrieval, or remote code execution depending on the available POP chain in the target environment.

Critical Impact

Unauthenticated attackers can exploit this PHP Object Injection vulnerability to potentially achieve remote code execution, delete arbitrary files, or access sensitive data when a POP chain is present on the target system.

Affected Products

• Database for Contact Form 7, WPforms, Elementor forms plugin for WordPress versions up to and including 1.4.7
• WordPress sites with additional plugins or themes containing POP chains (increased risk)
• WordPress contact-form-entries plugin

Discovery Timeline

• 2026-03-05 - CVE-2026-2599 published to NVD
• 2026-03-05 - Last updated in NVD database

Technical Details for CVE-2026-2599

Vulnerability Analysis

This vulnerability is classified as CWE-502 (Deserialization of Untrusted Data). The core issue lies in the plugin's handling of user-supplied data within the CSV download functionality. The download_csv function accepts serialized data from untrusted sources and passes it directly to PHP's deserialization functions without implementing proper input validation or sanitization measures.

PHP Object Injection vulnerabilities occur when an application deserializes user-controllable data, allowing attackers to manipulate the serialized object to control class properties. When combined with magic methods (__wakeup, __destruct, __toString, etc.) present in other installed plugins or themes, attackers can chain these methods to achieve malicious actions.

The vulnerability is particularly dangerous because it can be exploited by unauthenticated users over the network, requiring no special privileges or user interaction to trigger.

Root Cause

The root cause of CVE-2026-2599 is the insecure deserialization of untrusted input in the download_csv function located in contact-form-entries.php. The function fails to implement proper validation checks on incoming data before deserializing it, violating secure coding practices that mandate treating all user input as potentially malicious.

The vulnerable code sections can be found at lines 2972 and 3016 of the plugin source code.

Attack Vector

The attack is network-based and can be initiated remotely without authentication. An attacker crafts a malicious serialized PHP object and submits it to the vulnerable download_csv endpoint. When the application processes this request, it deserializes the malicious payload.

The attack complexity is low, as it does not require special access conditions or circumventing security measures. The vulnerability can be exploited to affect confidentiality, integrity, and availability depending on the POP chain available in the target WordPress installation. The attack may involve:

1. Identifying the vulnerable CSV download functionality
2. Crafting a serialized PHP object containing malicious properties
3. Submitting the payload to the vulnerable endpoint
4. If a suitable POP chain exists, the deserialization triggers the chain leading to code execution, file manipulation, or data exfiltration

Detection Methods for CVE-2026-2599

Indicators of Compromise

• Unusual HTTP POST requests to WordPress CSV download endpoints containing serialized PHP object patterns (e.g., O: prefix in request parameters)
• Unexpected file deletions or modifications on WordPress servers
• Anomalous outbound network connections from web servers
• PHP error logs showing deserialization-related warnings or object instantiation errors

Detection Strategies

• Monitor web application logs for requests containing serialized PHP object signatures targeting the contact-form-entries plugin endpoints
• Implement Web Application Firewall (WAF) rules to detect and block serialized PHP object patterns in HTTP request parameters
• Deploy endpoint detection solutions that monitor for unusual process spawning or file system activities following web requests
• Conduct regular plugin audits to identify installations of affected versions (≤1.4.7)

Monitoring Recommendations

• Enable verbose logging for WordPress plugin activities, particularly the Database for Contact Form 7, WPforms, Elementor forms plugin
• Configure SIEM alerts for HTTP requests containing suspicious serialization patterns (O:[0-9]+:, a:[0-9]+:, s:[0-9]+:)
• Monitor file integrity for critical WordPress directories to detect unauthorized modifications
• Track authentication and authorization events for anomalies following suspicious deserialization attempts

How to Mitigate CVE-2026-2599

Immediate Actions Required

• Update the Database for Contact Form 7, WPforms, Elementor forms plugin to version 1.4.8 or later immediately
• Audit all WordPress sites for installations of the vulnerable plugin version
• Review web server logs for evidence of exploitation attempts targeting the download_csv functionality
• Implement WAF rules to block serialized PHP object patterns in incoming requests as an interim measure

Patch Information

The vendor has released a security patch addressing this vulnerability. The fix can be verified in the WordPress Plugin Change Log (changeset 3474882). Site administrators should update to the latest version through the WordPress plugin update mechanism or by manually downloading the patched version from the WordPress plugin repository.

For detailed vulnerability information, refer to the Wordfence Vulnerability Report.

Workarounds

• Temporarily disable the Database for Contact Form 7, WPforms, Elementor forms plugin if immediate patching is not possible
• Restrict access to the plugin's administrative functions using .htaccess rules or server-level access controls
• Deploy a WAF with rules specifically designed to detect and block PHP Object Injection attempts
• Review and potentially remove unnecessary plugins or themes that may contain POP chains to reduce the attack surface

# Temporary access restriction for vulnerable endpoint (Apache)
# Add to .htaccess in WordPress root directory
<FilesMatch "contact-form-entries\.php">
    Order Deny,Allow
    Deny from all
    Allow from 127.0.0.1
    # Add trusted admin IP addresses
    # Allow from YOUR.ADMIN.IP.ADDRESS
</FilesMatch>