CVE-2026-40725: WooCommerce Filters Auth Bypass Flaw

CVE-2026-40725 Overview

CVE-2026-40725 is an unauthenticated PHP Object Injection vulnerability affecting the WooCommerce Product Filters plugin for WordPress in versions prior to 2.0.6. The flaw stems from insecure deserialization of untrusted input [CWE-502] and can be triggered remotely by any unauthenticated visitor. Successful exploitation allows attackers to instantiate arbitrary PHP objects and abuse existing gadget chains within the WordPress runtime to achieve remote code execution, data tampering, or full site compromise.

Critical Impact
Unauthenticated attackers can inject malicious serialized PHP objects over the network, leading to high-impact compromise of confidentiality, integrity, and availability on affected WordPress sites.

Affected Products

WooCommerce Product Filters plugin for WordPress
All versions prior to 2.0.6
WordPress installations using the vulnerable plugin in e-commerce deployments

Discovery Timeline

2026-06-17 - CVE-2026-40725 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2026-40725

Vulnerability Analysis

The vulnerability resides in how the WooCommerce Product Filters plugin processes attacker-controlled input that is passed to PHP's unserialize() routine. Because the plugin accepts serialized data on endpoints reachable without authentication, an attacker can submit a crafted payload that triggers object instantiation during deserialization.

PHP Object Injection becomes exploitable when the application loads classes that define magic methods such as __wakeup, __destruct, or __toString with side effects. WordPress and WooCommerce ship many such classes, providing gadget chains that turn deserialization into file writes, SQL execution, or command execution. The unauthenticated network reachability removes the need for an account or social engineering step.

Root Cause

The root cause is unsafe deserialization of untrusted input [CWE-502]. The plugin does not validate, sign, or restrict the structure of serialized data before passing it to unserialize(). Any class autoloaded by WordPress or active plugins becomes reachable, expanding the gadget surface beyond the plugin's own code.

Attack Vector

The attack vector is network-based with no privileges and no user interaction required. An attacker sends an HTTP request containing a crafted serialized PHP object to a plugin endpoint that accepts filter parameters. The server deserializes the payload, instantiates the attacker-chosen class, and executes its magic methods in the WordPress process context.

The vulnerability mechanism follows the standard PHP Object Injection pattern: attacker-supplied serialized data flows into unserialize(), magic methods on instantiated objects fire automatically, and chained gadgets convert object construction into arbitrary code or filesystem operations. See the Patchstack WooCommerce Plugin Vulnerability advisory for additional technical context.

Detection Methods for CVE-2026-40725

Indicators of Compromise

HTTP requests to WooCommerce Product Filters endpoints containing serialized PHP markers such as O:, a:, or s: followed by length and class names.
Unexpected PHP errors referencing __wakeup, __destruct, or unserialize() in web server or PHP-FPM logs.
New or modified files in wp-content/uploads, wp-content/plugins, or theme directories created by the web server user without a corresponding admin action.
Outbound network connections initiated by the PHP-FPM or Apache worker process to unfamiliar hosts.

Detection Strategies

Inspect web access logs for query strings and POST bodies containing PHP serialization signatures targeting filter, AJAX, or REST endpoints of the plugin.
Monitor for child processes spawned by the web server such as sh, bash, python, or curl, which indicate post-exploitation activity.
Alert on file integrity changes to PHP files under wp-content/ and on the creation of unexpected .php files in upload directories.

Monitoring Recommendations

Enable verbose logging for the WooCommerce Product Filters plugin and forward web server logs to a central analytics platform.
Correlate WAF events tagged as PHP Object Injection with endpoint process telemetry to confirm exploitation attempts.
Track WordPress plugin inventory and version drift across all hosted sites to identify exposed instances of versions below 2.0.6.

How to Mitigate CVE-2026-40725

Immediate Actions Required

Update the WooCommerce Product Filters plugin to version 2.0.6 or later on every WordPress site in the environment.
Audit recent web server, PHP, and WordPress logs for serialized payloads or anomalous filter requests before the upgrade window.
Rotate WordPress administrator passwords, secret keys in wp-config.php, and API tokens if exploitation indicators are present.
Review installed plugins and themes for unauthorized modifications or newly added PHP files.

Patch Information

The vendor has addressed the issue in WooCommerce Product Filters version 2.0.6. Refer to the Patchstack WooCommerce Plugin Vulnerability advisory for vendor remediation details and version metadata.

Workarounds

Deactivate the WooCommerce Product Filters plugin until patching is complete if immediate upgrade is not possible.
Deploy a web application firewall rule that blocks request bodies and query parameters containing PHP serialization patterns such as O:\d+: and a:\d+:{.
Restrict access to plugin endpoints by IP allowlist at the reverse proxy layer where feasible.
Disable unused plugins and themes to reduce the number of autoloadable gadget classes available to a deserialization payload.

bash

# Configuration example: WP-CLI update workflow
wp plugin update woocommerce-product-filters --version=2.0.6
wp plugin get woocommerce-product-filters --field=version
wp plugin deactivate woocommerce-product-filters   # fallback if patch cannot be applied