CVE-2021-47712
📋 TL;DR
A cryptography vulnerability in Kentico Xperience allows attackers to manipulate URL hash values, potentially enabling unauthorized actions or data access. This affects all Kentico Xperience deployments using the vulnerable hashing mechanism.
💻 Affected Systems
- Kentico Xperience
📦 What is this software?
Xperience by Kentico
⚠️ Risk & Real-World Impact
Worst Case
Attackers could bypass authentication, escalate privileges, or manipulate application data by forging valid URL hashes.
Likely Case
Session hijacking, unauthorized access to restricted content, or parameter tampering attacks.
If Mitigated
Limited impact with proper input validation and hash verification controls in place.
🎯 Exploit Status
Requires understanding of Kentico's hashing mechanism but no authentication needed for URL manipulation attacks.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Hotfix available - specific version not provided
Vendor Advisory: https://devnet.kentico.com/download/hotfixes
Restart Required: Yes
Instructions:
1. Download hotfix from Kentico DevNet 2. Apply hotfix according to Kentico documentation 3. Restart application/services 4. Verify hash validation is working
🔧 Temporary Workarounds
Disable URL hashing
allTemporarily disable vulnerable URL hashing functionality if not critical
Configuration dependent - modify Kentico web.config or settings
Implement WAF rules
allAdd web application firewall rules to detect and block hash manipulation attempts
WAF-specific configuration required
🧯 If You Can't Patch
- Implement additional server-side validation of all URL parameters and hashes
- Monitor logs for unusual hash patterns or failed validation attempts
🔍 How to Verify
Check if Vulnerable:
Test if URL hash values can be manipulated while maintaining application acceptanceCheck Version:
Check Kentico administration interface or web.config for version informationVerify Fix Applied:
Verify hotfix applied and test that manipulated hashes are rejected📡 Detection & Monitoring
Log Indicators:
- Failed hash validation attempts
- Unusual URL parameter patterns
- Authentication failures from valid sessions
Network Indicators:
- Repeated requests with modified hash parameters
- Unusual parameter combinations in URLs
SIEM Query:
web_requests WHERE url CONTAINS 'hash=' AND status_code IN (400, 403, 500) GROUP BY source_ip