CVE-2026-76547 Overview
CVE-2026-76547 is a PHP Object Injection vulnerability in the User Profile Builder WordPress plugin in versions before 4.0.1. The plugin fails to validate the type of data being deserialized when importing a configuration file. Administrators or other high-privilege users can trigger insecure deserialization by uploading a crafted configuration file. The affected feature is a free add-on that is disabled by default. The plugin itself does not ship a POP (property-oriented programming) chain, so additional impact requires a suitable gadget from another installed plugin or theme.
Critical Impact
Authenticated administrators can deserialize attacker-controlled PHP objects, enabling code execution or data compromise when a gadget chain is available in the environment.
Affected Products
- User Profile Builder WordPress plugin versions prior to 4.0.1
- WordPress installations with the optional import/export add-on enabled
- Sites with additional plugins or themes containing exploitable PHP gadget chains
Discovery Timeline
- 2026-08-29 - CVE-2026-76547 published to NVD
- 2026-08-31 - Last updated in NVD database
Technical Details for CVE-2026-76547
Vulnerability Analysis
The vulnerability is classified as Insecure Deserialization [CWE-502]. The import routine in the User Profile Builder plugin calls PHP's unserialize() on data read from an administrator-supplied configuration file without validating the expected object types. When an attacker with administrator privileges submits a crafted serialized payload, PHP instantiates arbitrary objects and invokes magic methods such as __wakeup() or __destruct() during object lifecycle events.
Because the plugin itself contains no usable POP chain, exploitation requires a gadget from a co-installed plugin, theme, or library. WordPress deployments commonly bundle libraries that expose viable chains, expanding the practical attack surface.
Root Cause
The root cause is the direct deserialization of untrusted input through unserialize() without an allow-list of permitted classes. Modern PHP supports the allowed_classes option to constrain deserialization, but the affected code path does not use it. The vulnerable feature is delivered as a free add-on and remains disabled by default, which reduces the exposed population but does not remove the underlying flaw.
Attack Vector
An attacker must first obtain administrator credentials or otherwise reach the plugin's import functionality. The attacker then uploads a configuration file containing a serialized PHP object payload aligned with a gadget chain present on the target site. Deserialization triggers method calls that can lead to arbitrary file writes, command execution, SQL injection, or authentication bypass depending on the gadget available.
The vulnerability manifests in the plugin's configuration import handler. Consult the WPScan Vulnerability Report for further technical detail.
Detection Methods for CVE-2026-76547
Indicators of Compromise
- Unexpected configuration import events in the User Profile Builder admin interface prior to patching to version 4.0.1.
- Newly created PHP files or modified theme and plugin files following an administrator import action.
- Outbound network connections initiated by the web server process shortly after a plugin configuration upload.
- New administrator accounts, altered WordPress options, or unexpected scheduled tasks in wp_options and wp_users.
Detection Strategies
- Inspect web server access logs for POST requests to User Profile Builder import endpoints from unusual source addresses.
- Scan uploaded configuration files for serialized PHP object markers such as O: and C: patterns.
- Monitor for PHP process spawning shell utilities, which is atypical for WordPress request handling.
- Baseline plugin file integrity and alert on modifications to wp-content/plugins/ and wp-content/themes/.
Monitoring Recommendations
- Enable audit logging for administrator actions, including plugin configuration imports and settings changes.
- Forward WordPress and web server logs to a centralized analytics platform for correlation and retention.
- Track authentication events for administrator accounts and alert on logins from new geographies or user agents.
How to Mitigate CVE-2026-76547
Immediate Actions Required
- Update the User Profile Builder plugin to version 4.0.1 or later on all WordPress sites.
- Disable the configuration import add-on if it is not required for operations.
- Audit administrator accounts and rotate credentials for any account with plugin management rights.
- Review recent import activity and file changes across wp-content/ for signs of exploitation.
Patch Information
The vendor addressed the vulnerability in User Profile Builder version 4.0.1 by validating deserialized data types during configuration import. Refer to the WPScan Vulnerability Report for advisory details.
Workarounds
- Restrict administrator access using multi-factor authentication and IP allow-listing for the WordPress admin interface.
- Remove or deactivate the import/export add-on until the plugin is upgraded to a fixed release.
- Apply a web application firewall rule to block requests containing serialized PHP object patterns to plugin admin endpoints.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
