CVE-2026-25431: WPMU DEV Hustle Auth Bypass Vulnerability

CVE-2026-25431 Overview

CVE-2026-25431 is a missing authorization vulnerability in the WPMU DEV Hustle plugin for WordPress. The flaw affects all versions of Hustle up to and including 7.8.10.1. The plugin fails to enforce proper access control checks, allowing unauthenticated network attackers to interact with functionality that should be restricted. The issue is classified under CWE-862: Missing Authorization and stems from incorrectly configured access control security levels within the plugin. Successful exploitation results in limited integrity impact without requiring user interaction or authentication.

Critical Impact

Unauthenticated attackers can reach restricted plugin functionality over the network due to broken access control, affecting integrity of data managed by the Hustle plugin.

Affected Products

• WPMU DEV Hustle plugin for WordPress
• All Hustle versions through 7.8.10.1
• WordPress sites running the vulnerable plugin (also known as WordPress Popup)

Discovery Timeline

• 2026-05-12 - CVE-2026-25431 published to NVD
• 2026-05-13 - Last updated in NVD database

Technical Details for CVE-2026-25431

Vulnerability Analysis

The Hustle plugin provides popups, opt-ins, and email marketing features for WordPress sites. CVE-2026-25431 results from missing authorization checks on one or more plugin endpoints. The plugin assigns access control security levels incorrectly, leaving privileged operations reachable without proper capability validation. Attackers can send crafted requests over the network and trigger actions intended for authenticated or higher-privileged users. The CVSS vector indicates impact is limited to integrity, with no confidentiality or availability loss observed. The attack is reachable remotely, requires no privileges, and needs no user interaction, expanding the pool of potential exploiters to any unauthenticated client that can reach the WordPress site.

Root Cause

The root cause is the absence or misconfiguration of authorization checks in plugin request handlers. WordPress plugins typically gate sensitive actions with current_user_can() checks and nonce validation. In Hustle through 7.8.10.1, one or more handlers fail to enforce these controls at the correct security level, allowing requests to proceed regardless of the requester's role.

Attack Vector

An unauthenticated attacker sends HTTP requests directly to the vulnerable plugin endpoints exposed by the WordPress site. Because the plugin does not validate the caller's capability, the request executes and modifies plugin-managed data. No special tooling or local access is required. See the Patchstack Vulnerability Report for additional technical context.

Detection Methods for CVE-2026-25431

Indicators of Compromise

• Unexpected modifications to Hustle plugin configurations, modules, or campaign data without a corresponding administrator session
• HTTP requests to Hustle plugin AJAX or REST endpoints originating from unauthenticated sessions or anonymous IP addresses
• New or altered popup, opt-in, or email module entries that do not map to known admin activity

Detection Strategies

• Audit web server access logs for requests to Hustle plugin endpoints (paths containing wordpress-popup or hustle) that lack valid authentication cookies
• Compare plugin database tables against known-good backups to identify unauthorized changes
• Review WordPress audit logs for plugin actions performed without an associated logged-in user

Monitoring Recommendations

• Enable verbose logging on the WordPress site and forward logs to a centralized analytics platform for query and alerting
• Alert on spikes in anonymous requests to plugin endpoints, especially POST requests modifying state
• Monitor file integrity for the Hustle plugin directory and database rows associated with the plugin

How to Mitigate CVE-2026-25431

Immediate Actions Required

• Identify all WordPress sites with the WPMU DEV Hustle plugin installed and confirm the installed version
• Update Hustle to a version released after 7.8.10.1 that addresses the missing authorization issue
• Restrict access to the WordPress admin and AJAX endpoints with a web application firewall (WAF) rule until patching completes

Patch Information

The vulnerability affects Hustle through 7.8.10.1. Administrators should consult the Patchstack advisory and the WPMU DEV plugin changelog for the fixed release and apply the latest version through the WordPress plugin updater.

Workarounds

• Temporarily deactivate the Hustle plugin on sites that cannot be updated immediately
• Block unauthenticated access to plugin-specific AJAX and REST routes at the WAF or reverse proxy layer
• Limit administrative endpoint access by source IP where operationally feasible

# Example WAF rule snippet to block unauthenticated POSTs to Hustle endpoints
# (adapt to your WAF syntax)
SecRule REQUEST_URI "@rx /wp-admin/admin-ajax\.php" \
  "chain,deny,status:403,id:1002601,msg:'Block unauth Hustle action'"
SecRule ARGS:action "@rx ^hustle_" "chain"
SecRule &REQUEST_COOKIES:/wordpress_logged_in_/ "@eq 0"