CVE-2026-11913: Drupal Mother May I XSS Vulnerability

CVE-2026-11913 Overview

CVE-2026-11913 is a Cross-Site Scripting (XSS) vulnerability [CWE-79] in the Drupal Mother May I contributed module. The flaw allows attackers to inject malicious script content that executes in the context of other users' browsers. The vulnerability is exploitable over the network without authentication or user interaction, and impacts confidentiality, integrity, and availability of affected Drupal installations.

Critical Impact
Unauthenticated attackers can inject arbitrary JavaScript into Drupal pages served by the Mother May I module, enabling session hijacking, credential theft, and administrative account takeover.

Affected Products

Drupal Mother May I contributed module (all affected versions per vendor advisory)
Drupal sites with the Mother May I module installed and enabled
Refer to the Drupal Security Advisory for the specific version ranges

Discovery Timeline

2026-07-10 - CVE-2026-11913 published to the National Vulnerability Database
2026-07-13 - Last updated in NVD database

Technical Details for CVE-2026-11913

Vulnerability Analysis

The vulnerability is a Cross-Site Scripting flaw classified under [CWE-79] (Improper Neutralization of Input During Web Page Generation). The Mother May I module fails to properly sanitize or encode user-supplied input before rendering it in HTML output. As a result, attacker-controlled data is interpreted by browsers as executable script.

Exploitation requires only network access to a vulnerable Drupal site. No prior authentication or victim interaction beyond visiting a crafted page is required to trigger script execution in the browser context. Successful exploitation lets attackers steal session cookies, perform actions as authenticated users, deface content, or pivot to administrative takeover if a privileged user views the malicious payload.

Root Cause

The root cause is missing or insufficient output encoding on user-controllable fields handled by the Mother May I module. Drupal's rendering pipeline provides safe output mechanisms, but the module rendered attacker-controlled values without applying them, allowing raw HTML and JavaScript to reach the DOM.

Attack Vector

An attacker submits a crafted payload containing HTML or JavaScript through an input surface exposed by the Mother May I module. When the module later renders that value in a page, the payload executes in the browser of any user who loads the affected view. Because the attack vector is network-based and requires no privileges, exploitation can be automated at scale against exposed Drupal endpoints.

Refer to the Drupal Security Advisory for module-specific reproduction details.

Detection Methods for CVE-2026-11913

Indicators of Compromise

HTTP requests to Mother May I module endpoints containing <script>, javascript:, onerror=, or onload= payloads
Unexpected outbound requests from user browsers to attacker-controlled domains after visiting Drupal pages
Drupal watchdog or web server logs showing encoded payloads such as %3Cscript%3E in query strings or POST bodies
New or modified Drupal admin sessions originating from unusual IP addresses following user visits to module-rendered pages

Detection Strategies

Inspect Drupal access logs for requests targeting Mother May I routes with script-like content in parameters
Deploy a Web Application Firewall rule set covering OWASP CRS XSS signatures in front of the Drupal site
Enable a strict Content Security Policy and monitor report-uri or report-to violations for inline script blocks
Compare rendered HTML from module views against expected output to identify unencoded user input

Monitoring Recommendations

Forward Drupal, PHP, and web server logs to a centralized SIEM for correlation and long-term retention
Alert on repeated 200-response requests to module endpoints containing HTML control characters
Monitor authenticated admin session creation events for anomalies immediately after XSS-suspect requests
Track browser CSP violation reports to detect ongoing injection attempts against production users

How to Mitigate CVE-2026-11913

Immediate Actions Required

Apply the fixed version of the Mother May I module referenced in the Drupal Security Advisory
Disable the Mother May I module until patching is complete if it is not business-critical
Invalidate active administrator sessions and rotate credentials for privileged Drupal accounts
Review recent module-related requests in access logs for evidence of exploitation attempts

Patch Information

The Drupal Security Team has published a fixed release for the Mother May I contributed module. Administrators should upgrade to the version specified in advisory SA-CONTRIB-2026-045. Update the module through Composer or the Drupal update manager, then run drush updatedb and clear the site cache to complete deployment.

Workarounds

Restrict access to Mother May I module endpoints through web server or reverse proxy access control lists until patched
Deploy a WAF signature blocking common XSS payloads on module URIs as a compensating control
Enforce a strict Content Security Policy that disallows inline scripts and untrusted script sources
Limit permissions on Drupal roles that can submit content processed by the module to trusted users only

bash

# Update the Mother May I module using Composer and apply database updates
composer update drupal/mother_may_i --with-dependencies
drush updatedb -y
drush cache:rebuild