CVE-2025-32036
📋 TL;DR
CVE-2025-32036 is a captcha bypass vulnerability in DNN CMS where the generated captcha images have insufficient complexity, allowing Optical Character Recognition (OCR) tools to automatically read them. This enables attackers to bypass captcha protection and perform automated attacks like credential stuffing or form spam. All DNN installations using the vulnerable captcha implementation are affected.
💻 Affected Systems
- DNN Platform (formerly DotNetNuke)
📦 What is this software?
Dotnetnuke by Dnnsoftware
⚠️ Risk & Real-World Impact
Worst Case
Attackers bypass captcha protection to perform automated attacks at scale, including credential stuffing, account takeover, form spam, and denial of service through automated requests.
Likely Case
Automated bots bypass captcha to perform credential stuffing attacks, spam form submissions, or scrape protected content.
If Mitigated
With proper monitoring and rate limiting, impact is limited to increased spam or failed login attempts that can be detected and blocked.
🎯 Exploit Status
Exploitation requires basic OCR tools and programming knowledge to automate requests. No authentication needed as captcha is typically used on public-facing forms.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 9.13.8
Vendor Advisory: https://github.com/dnnsoftware/Dnn.Platform/security/advisories/GHSA-48q9-3p26-8595
Restart Required: Yes
Instructions:
1. Backup your DNN installation and database. 2. Download DNN Platform version 9.13.8 or later from the official repository. 3. Follow the DNN upgrade documentation to apply the update. 4. Restart the application pool in IIS. 5. Verify the update was successful.
🔧 Temporary Workarounds
Implement alternative captcha solution
allReplace DNN's built-in captcha with a third-party service like reCAPTCHA or hCaptcha that uses more sophisticated anti-bot mechanisms.
Enable rate limiting
allImplement request rate limiting on forms using captcha to reduce impact of automated attacks even if captcha is bypassed.
🧯 If You Can't Patch
- Implement Web Application Firewall (WAF) rules to detect and block automated form submissions
- Add additional authentication factors or challenge-response mechanisms for sensitive forms
🔍 How to Verify
Check if Vulnerable:
Check DNN version in Host Settings > Basic Settings. If version is below 9.13.8 and using built-in captcha, the system is vulnerable.Check Version:
Check the 'Version' field in Host Settings > Basic Settings in DNN admin panelVerify Fix Applied:
After upgrading to 9.13.8 or later, verify the version in Host Settings and test that captcha images appear more complex and randomized.📡 Detection & Monitoring
Log Indicators:
- High volume of form submissions from single IPs
- Unusual patterns in failed captcha attempts
- Spike in automated form completions
Network Indicators:
- Repeated POST requests to forms with captcha
- Consistent timing between form submissions
- Requests from known bot IP ranges
SIEM Query:
source="iis" AND (url="*/captcha.aspx" OR message="*captcha*") | stats count by src_ip, url