CVE-2026-4882: WordPress URAF Plugin RCE Vulnerability

CVE-2026-4882 Overview

CVE-2026-4882 is an unauthenticated arbitrary file upload vulnerability in the User Registration Advanced Fields plugin for WordPress. The flaw exists in the URAF_AJAX::method_upload function and affects all versions up to and including 1.6.20. The plugin fails to validate file types during upload, allowing attackers to place arbitrary files on the server. Successful exploitation can lead to remote code execution on the WordPress host. Exploitation requires that a Profile Picture field be configured on a registration form, which is a common configuration on sites using this plugin.

Critical Impact

Unauthenticated remote attackers can upload executable files to vulnerable WordPress sites and achieve remote code execution when a Profile Picture field is present in the registration form.

Affected Products

• WordPress User Registration Advanced Fields plugin versions up to and including 1.6.20
• WordPress sites with a Profile Picture field added to a registration form
• Any WordPress installation exposing the plugin's URAF_AJAX::method_upload AJAX endpoint

Discovery Timeline

• 2026-05-02 - CVE-2026-4882 published to the National Vulnerability Database
• 2026-05-05 - Last updated in the NVD database

Technical Details for CVE-2026-4882

Vulnerability Analysis

The vulnerability is classified as Unrestricted Upload of File with Dangerous Type [CWE-434]. The plugin exposes an AJAX action handled by URAF_AJAX::method_upload that accepts file uploads tied to the Profile Picture field in registration forms. The handler does not enforce server-side file type validation, MIME checks, or extension allow-listing before writing the uploaded payload to disk inside the WordPress uploads directory.

Because the AJAX endpoint is reachable without authentication, any remote actor can submit crafted multipart requests containing PHP, .phtml, or other server-executable content. Once the file lands in a web-accessible path, the attacker requests it directly to trigger code execution under the web server user context. The end result is full compromise of the WordPress instance, including database access, credential theft, and the ability to pivot to adjacent infrastructure.

Root Cause

The root cause is missing file type validation in the URAF_AJAX::method_upload function. The handler relies on client-controlled metadata rather than verifying the actual file type against an allow-list of safe image formats expected for a profile picture upload.

Attack Vector

The attack vector is network-based and requires no privileges or user interaction. An unauthenticated attacker identifies a target WordPress site running a vulnerable version with a registration form containing a Profile Picture field. The attacker submits a malicious file to the plugin's upload AJAX endpoint and then issues an HTTP request to the resulting URL to execute the payload. Refer to the Wordfence Vulnerability Report for additional technical context.

Detection Methods for CVE-2026-4882

Indicators of Compromise

• Unexpected files with executable extensions such as .php, .phtml, or .phar written under wp-content/uploads/ paths used by the User Registration Advanced Fields plugin
• POST requests to admin-ajax.php invoking the URAF_AJAX::method_upload action from unauthenticated sessions
• New administrator accounts, modified wp-config.php, or webshell artifacts following file upload activity
• Outbound connections from the web server to attacker-controlled infrastructure shortly after upload events

Detection Strategies

• Inspect web server logs for POST requests to wp-admin/admin-ajax.php containing the plugin's upload action without an authenticated session cookie
• Hunt for files in WordPress upload directories whose magic bytes do not match their extension or whose extensions are not standard image formats
• Correlate file-write events in the WordPress uploads directory with subsequent GET requests to the same file path

Monitoring Recommendations

• Enable file integrity monitoring on the wp-content/uploads/ directory and alert on creation of non-image file types
• Forward web server access logs and PHP error logs to a centralized logging platform for sustained query and retention
• Monitor outbound traffic from web servers for connections to unfamiliar destinations, which can indicate post-exploitation callback activity

How to Mitigate CVE-2026-4882

Immediate Actions Required

• Update the User Registration Advanced Fields plugin to a version newer than 1.6.20 as soon as the vendor releases a fix
• Audit registration forms and temporarily remove the Profile Picture field if patching cannot be completed promptly
• Review WordPress upload directories for unauthorized files and remove any webshells or suspicious payloads
• Rotate WordPress administrator credentials, secret keys in wp-config.php, and any database credentials that may have been exposed

Patch Information

At the time of NVD publication, all versions up to and including 1.6.20 are listed as vulnerable. Refer to the WP User Registration product page and the Wordfence Vulnerability Report for the latest fixed version and vendor advisory details.

Workarounds

• Remove the Profile Picture field from all active registration forms, since exploitation is conditional on this field being present
• Restrict access to wp-admin/admin-ajax.php from untrusted networks using a web application firewall ruleset
• Configure the web server to deny PHP execution within wp-content/uploads/ to prevent uploaded files from being interpreted as code
• Disable the plugin entirely until a patched version is installed if the Profile Picture functionality is not business-critical

# Apache: deny PHP execution within the WordPress uploads directory
# Place the following in wp-content/uploads/.htaccess
<FilesMatch "\.(php|phtml|phar|php3|php4|php5|php7|phps)$">
    Require all denied
</FilesMatch>