CVE-2021-34675
📋 TL;DR
CVE-2021-34675 is an authentication bypass vulnerability in Basix NEX-Forms WordPress plugin that allows unauthenticated attackers to access stored PDF reports without proper authentication. This affects WordPress sites using NEX-Forms through version 7.8.7. Attackers can potentially access sensitive form submission data stored in PDF format.
💻 Affected Systems
- Basix NEX-Forms WordPress Form Builder
📦 What is this software?
Nex Forms by Basixonline
⚠️ Risk & Real-World Impact
Worst Case
Unauthenticated attackers access sensitive user-submitted data including personal information, payment details, or confidential business data stored in PDF reports, leading to data breach and regulatory violations.
Likely Case
Attackers access form submission data containing personal identifiable information (PII), contact details, or other sensitive user data submitted through vulnerable forms.
If Mitigated
With proper access controls and monitoring, unauthorized access attempts are detected and blocked before sensitive data is exfiltrated.
🎯 Exploit Status
Public proof-of-concept code exists on GitHub, and the vulnerability requires no authentication, making exploitation straightforward.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 7.8.8 and later
Vendor Advisory: http://basixonline.net/nex-forms-wordpress-form-builder-demo/change-log/
Restart Required: No
Instructions:
1. Log into WordPress admin panel. 2. Navigate to Plugins → Installed Plugins. 3. Find NEX-Forms and click 'Update Now'. 4. Alternatively, download version 7.8.8+ from WordPress repository and manually update.
🔧 Temporary Workarounds
Disable PDF Report Feature
allTemporarily disable PDF report generation functionality in NEX-Forms settings
Restrict Access via .htaccess
linuxBlock access to PDF report directories using web server configuration
# Add to .htaccess in WordPress root:
<FilesMatch "\.(pdf)$">
Order Deny,Allow
Deny from all
</FilesMatch>
🧯 If You Can't Patch
- Disable NEX-Forms plugin entirely until patched
- Implement web application firewall (WAF) rules to block PDF report access attempts
🔍 How to Verify
Check if Vulnerable:
Check WordPress admin → Plugins → Installed Plugins for NEX-Forms version. If version is 7.8.7 or earlier, system is vulnerable.Check Version:
wp plugin list --name=nex-forms --field=version (if WP-CLI installed)Verify Fix Applied:
Verify NEX-Forms plugin version is 7.8.8 or later in WordPress admin panel.📡 Detection & Monitoring
Log Indicators:
- Unusual access to PDF files in uploads/nex-forms directory
- Multiple failed authentication attempts followed by PDF access
- Direct requests to PDF report URLs without session cookies
Network Indicators:
- HTTP GET requests to /wp-content/uploads/nex-forms/*.pdf from unauthenticated sources
- Unusual spikes in PDF file downloads from form submission directories
SIEM Query:
source="web_server" AND (url="*.pdf" AND NOT user_agent="*bot*" AND NOT referer="*admin*")