CVE-2025-59903
📋 TL;DR
A stored Cross-Site Scripting (XSS) vulnerability in Kubysoft allows attackers to upload malicious SVG images containing embedded scripts. These scripts execute automatically when users view the compromised images, potentially stealing session cookies or performing actions on behalf of victims. All Kubysoft users who can upload or view SVG files are affected.
💻 Affected Systems
- Kubysoft
📦 What is this software?
Kubysoft by Kubysoft
⚠️ Risk & Real-World Impact
Worst Case
Attackers could steal administrator credentials, hijack user sessions, deface websites, or redirect users to malicious sites, potentially leading to complete system compromise.
Likely Case
Attackers will steal user session cookies to impersonate victims, perform unauthorized actions, or deploy malware through the compromised application.
If Mitigated
With proper input validation and output encoding, malicious scripts would be neutralized, preventing execution while preserving legitimate SVG functionality.
🎯 Exploit Status
Exploitation requires ability to upload SVG files; authenticated users or those with upload privileges can exploit.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check vendor advisory for specific version
Vendor Advisory: https://www.incibe.es/en/incibe-cert/notices/aviso/multiple-vulnerabilities-kubysoft
Restart Required: Yes
Instructions:
1. Review vendor advisory for patch details. 2. Apply the latest security update from Kubysoft. 3. Restart the application/service. 4. Verify SVG upload functionality is properly sanitized.
🔧 Temporary Workarounds
Disable SVG Uploads
allTemporarily block SVG file uploads through configuration or web server rules
# Configure web server to reject SVG uploads
# Example for Apache: AddType application/octet-stream .svg
# Example for Nginx: location ~ \.svg$ { deny all; }
Implement Content Security Policy
allAdd CSP headers to restrict script execution from untrusted sources
# Add to web server config: Content-Security-Policy: default-src 'self'; script-src 'self'
🧯 If You Can't Patch
- Implement strict input validation to sanitize SVG files before storage
- Configure web application firewall to detect and block malicious SVG content
🔍 How to Verify
Check if Vulnerable:
Test by uploading an SVG file containing <script>alert('XSS')</script> and checking if script executes when viewedCheck Version:
Check Kubysoft admin panel or configuration files for version informationVerify Fix Applied:
Attempt the same test after patching; script should not execute and SVG should display normally📡 Detection & Monitoring
Log Indicators:
- Unusual SVG file uploads
- Large number of SVG uploads from single IP
- SVG files with script tags in content
Network Indicators:
- SVG files containing script tags in upload traffic
- Unexpected JavaScript execution from SVG resources
SIEM Query:
source="web_logs" AND (file_extension="svg" AND (content="<script" OR content="javascript:"))