CVE-2025-11436
📋 TL;DR
This vulnerability in JhumanJ OpnForm up to version 1.9.3 allows remote attackers to upload arbitrary files without restrictions via the /answer endpoint. This could lead to server compromise, data theft, or malware deployment. All OpnForm installations up to 1.9.3 are affected.
💻 Affected Systems
- JhumanJ OpnForm
📦 What is this software?
Opnform by Jhumanj
⚠️ Risk & Real-World Impact
Worst Case
Complete server takeover through webshell upload leading to data exfiltration, ransomware deployment, or use as attack platform
Likely Case
Malicious file upload leading to defacement, data manipulation, or limited server access
If Mitigated
File upload attempts blocked or logged with no successful exploitation
🎯 Exploit Status
Public exploit details available; manipulation of /answer endpoint leads to unrestricted upload
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version after commit 95c3e23856465d202e6aec10bdb6ee0688b5305a
Vendor Advisory: https://github.com/JhumanJ/OpnForm/pull/900/commits/95c3e23856465d202e6aec10bdb6ee0688b5305a
Restart Required: No
Instructions:
1. Update OpnForm to latest version 2. Apply commit 95c3e23856465d202e6aec10bdb6ee0688b5305a 3. Verify file upload restrictions are properly implemented
🔧 Temporary Workarounds
Block /answer endpoint
allTemporarily block access to vulnerable endpoint via web server configuration
# For Apache: RewriteRule ^/answer - [F]
# For Nginx: location /answer { deny all; }
Implement file upload restrictions
allAdd server-side file type validation and size limits
# Configure web server to restrict uploads
# Example: Limit file types and sizes in application config
🧯 If You Can't Patch
- Implement WAF rules to block malicious file upload patterns
- Monitor and alert on file upload attempts to /answer endpoint
🔍 How to Verify
Check if Vulnerable:
Check if OpnForm version is ≤1.9.3 and test file upload to /answer endpointCheck Version:
Check OpnForm version in application configuration or package managerVerify Fix Applied:
Attempt file upload to /answer endpoint; should be rejected with proper validation📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads to /answer endpoint
- Large or suspicious file uploads
- Failed file validation attempts
Network Indicators:
- POST requests to /answer with file uploads
- Unusual file types being uploaded
SIEM Query:
source="web_logs" AND uri="/answer" AND method="POST" AND (file_upload="true" OR content_type="multipart/form-data")🔗 References
- https://docs.google.com/document/d/1GUjJA9vUbsXUngAv6ySsbCIhVynf8_djardLZYEDOe0/edit?tab=t.0#heading=h.dm5ttliupfqn
- https://github.com/JhumanJ/OpnForm/pull/900/commits/95c3e23856465d202e6aec10bdb6ee0688b5305a
- https://vuldb.com/?ctiid.327373
- https://vuldb.com/?id.327373
- https://vuldb.com/?submit.666877
