CVE-2026-108515 in Drupal
Summary
by MITRE • 10/30/2026
Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting") vulnerability in Drupal Drupal core allows Cross-Site Scripting (XSS). This issue affects Drupal core versions: from 8.9.0 to 10.6.19, from 11.0.0 to 11.3.19, from 11.4.0 to 11.4.10, from 12.0.0-alpha1 to 12.0.0-beta2.
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Analysis
by VulDB Data Team • 10/30/2026
The identified vulnerability represents a critical security flaw within the Drupal core content management system, classified under CWE-79 as Improper Neutralization of Input During Web Page Generation, commonly known as Cross-Site Scripting or XSS. This specific weakness allows an attacker to inject malicious client-side scripts into web pages viewed by other users. The scope of this vulnerability is extensive, impacting a wide range of Drupal versions including those from 8.9.0 through 10.6.19, and encompassing the newer major releases such as 11.0.0 up to 11.3.19, 11.4.0 through 11.4.10, and early access versions like 12.0.0-alpha1 to beta2. The presence of this flaw in both legacy stable branches and cutting-edge development releases indicates a systemic issue within the core input validation mechanisms that persists across different architectural iterations of the platform.
From a technical perspective, the vulnerability arises when user-supplied data is not adequately sanitized or encoded before being rendered into HTML output by the Drupal application. In typical web applications, inputs such as form submissions, URL parameters, or HTTP headers are processed and displayed to users without sufficient checks for malicious content like JavaScript code snippets. When an attacker crafts a request containing executable script tags or event handlers embedded within these input fields, the server processes the data normally but fails to strip out the harmful elements. Consequently, when another user accesses the affected page, their browser executes the injected scripts in the context of the trusted Drupal domain. This bypasses standard security controls such as the Same-Origin Policy, allowing the malicious script to access cookies, session tokens, and other sensitive information stored by the browser for that specific site.
The operational impact of this vulnerability is severe due to its potential for widespread exploitation via social engineering or automated campaigns. Attackers can leverage this flaw to perform account hijacking by stealing administrative credentials or user sessions, leading to unauthorized control over the website content and configuration. Beyond credential theft, the attacker may execute actions on behalf of the victim, such as modifying site settings, creating new administrator accounts, or defacing the public-facing interface. In enterprise environments where Drupal serves critical business functions, this can result in significant data breaches, reputational damage, and regulatory non-compliance with standards like GDPR or HIPAA that mandate strict protection of user privacy and data integrity. The ability to execute arbitrary JavaScript also opens avenues for further attacks such as keylogging, session fixation, or redirecting users to phishing sites designed to harvest additional sensitive information.
In terms of threat modeling and industry frameworks, this vulnerability aligns with the MITRE ATT&CK technique T1059.007, which covers Command and Scripting Interpreter: JavaScript. It also relates to initial access vectors where attackers might use malicious links embedded in emails or other platforms to trigger the XSS payload when a targeted user clicks through. The persistence of this issue across multiple major versions suggests that while Drupal has robust security practices, certain edge cases or specific modules interacting with core rendering pipelines may not have been fully hardened against sophisticated input manipulation techniques. This highlights the ongoing challenge in web development where dynamic content generation must balance flexibility for developers with rigorous sanitization protocols to prevent injection attacks.
To mitigate this risk, immediate action is required by upgrading all affected Drupal instances to a patched version that addresses these specific XSS vectors. Administrators should consult the official Drupal security advisory corresponding to their current version range to identify the exact patch release that resolves this issue. For environments where an upgrade is not immediately feasible due to compatibility constraints with custom modules or themes, temporary mitigations include implementing strict Content Security Policy headers to restrict script execution sources and deploying Web Application Firewalls configured to detect and block common XSS payloads in HTTP requests. Additionally, developers should review any custom code that handles user input to ensure it utilizes Drupal’s built-in sanitization functions such as check_plain or HTML Purifier libraries rather than relying on manual string manipulation which may be prone to errors. Regular security audits and penetration testing focused on injection vulnerabilities are recommended to maintain a strong defensive posture against evolving web application threats.