CVE-2026-3525: Drupal File Access Fix Auth Bypass Flaw

CVE-2026-3525 Overview

CVE-2026-3525 is an Incorrect Authorization vulnerability affecting the Drupal File Access Fix module (now deprecated). This vulnerability allows attackers to perform Forceful Browsing attacks, potentially bypassing access controls to access files that should be restricted.

Critical Impact

Attackers can bypass authorization controls to access protected files through forceful browsing techniques, potentially exposing sensitive data stored on affected Drupal installations.

Affected Products

• Drupal File Access Fix (deprecated) versions 0.0.0 through 1.1.x
• All installations using File Access Fix module prior to version 1.2.0

Discovery Timeline

• 2026-03-26 - CVE CVE-2026-3525 published to NVD
• 2026-03-26 - Last updated in NVD database

Technical Details for CVE-2026-3525

Vulnerability Analysis

This vulnerability is classified under CWE-863 (Incorrect Authorization), which occurs when the software performs an authorization check but does not correctly handle all cases, leading to incomplete protection. In the context of the Drupal File Access Fix module, the authorization mechanism fails to properly validate user permissions when certain file access requests are made.

The File Access Fix module was designed to address file access permission issues in Drupal, but ironically contains its own authorization flaw. When an attacker crafts specific requests to access files directly (forceful browsing), the module's authorization checks do not adequately prevent unauthorized access. This allows unauthenticated or low-privileged users to potentially access files that should be restricted based on Drupal's permission system.

Root Cause

The root cause lies in the incomplete implementation of authorization checks within the File Access Fix module. The module fails to properly validate access permissions for all file request paths, allowing certain direct URL requests to bypass the intended access controls. This is a classic example of broken access control where the authorization logic does not cover all possible access scenarios.

Attack Vector

The attack vector for this vulnerability is Forceful Browsing, where an attacker directly navigates to file URLs that should be protected. By manipulating URL paths or guessing file locations, attackers can bypass the authorization mechanisms and access restricted content. This type of attack does not require authentication and can be performed remotely through standard HTTP requests.

The vulnerability can be exploited by constructing direct URLs to files stored by Drupal. Since the File Access Fix module does not properly enforce access controls on all file requests, attackers can enumerate and access files by directly requesting their paths. For detailed technical information, refer to the Drupal Security Advisory.

Detection Methods for CVE-2026-3525

Indicators of Compromise

• Unusual file access patterns in web server logs showing direct file path requests
• Multiple sequential requests attempting to enumerate files in protected directories
• Access log entries showing successful file retrievals by unauthenticated users
• Spike in requests to /sites/default/files/ or similar Drupal file storage paths

Detection Strategies

• Monitor web server access logs for patterns indicating file enumeration attempts
• Implement web application firewall (WAF) rules to detect forceful browsing patterns
• Review Drupal watchdog logs for unauthorized file access attempts
• Deploy SentinelOne Singularity Platform to detect anomalous file access behavior on web servers

Monitoring Recommendations

• Enable comprehensive logging for the Drupal files directory
• Set up alerts for high-volume file access requests from single IP addresses
• Monitor for 200 OK responses to file requests from unauthenticated sessions
• Implement rate limiting on file access endpoints to slow enumeration attacks

How to Mitigate CVE-2026-3525

Immediate Actions Required

• Upgrade Drupal File Access Fix module to version 1.2.0 or later immediately
• If upgrade is not immediately possible, disable the File Access Fix module
• Review file access logs for evidence of exploitation
• Consider migrating to an actively maintained alternative module since this module is deprecated

Patch Information

The vulnerability has been addressed in File Access Fix version 1.2.0. Organizations should upgrade to this version or later. However, as this module is now deprecated, organizations should evaluate transitioning to alternative solutions for file access management in Drupal. For official patch details, refer to the Drupal Security Advisory.

Workarounds

• Temporarily disable the File Access Fix module until patching is possible
• Implement server-level access controls (e.g., .htaccess rules) to restrict direct file access
• Use web server configuration to require authentication for file directories
• Consider moving sensitive files outside the web root with a Drupal-controlled delivery mechanism

# Apache .htaccess configuration to restrict file access
# Place in sites/default/files/.htaccess
<FilesMatch ".*">
  Order Allow,Deny
  Deny from all
</FilesMatch>

# Allow specific file types if needed
<FilesMatch "\.(jpg|jpeg|png|gif|css|js)$">
  Order Deny,Allow
  Allow from all
</FilesMatch>