CVE-2021-45891
📋 TL;DR
This vulnerability in Softwarebuero Zauner ARC 4.2.0.4 allows attackers to escalate privileges within the application because all permission checks are performed client-side rather than server-side. Attackers can bypass intended access controls to gain unauthorized privileges. Organizations using this specific version of the software are affected.
💻 Affected Systems
- Softwarebuero Zauner ARC
📦 What is this software?
Arc by Zauner
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the application with administrative privileges, allowing data manipulation, unauthorized access to sensitive information, and potential lateral movement within the network.
Likely Case
Unauthorized privilege escalation leading to data access beyond user permissions, configuration changes, and potential data exfiltration.
If Mitigated
Limited impact with proper network segmentation and monitoring, though privilege escalation within the application remains possible.
🎯 Exploit Status
Exploitation requires initial access to the application but is straightforward once authenticated due to client-side permission checks.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.2.0.5 or later
Vendor Advisory: https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2021-063.txt
Restart Required: Yes
Instructions:
1. Contact Softwarebuero Zauner for the latest patched version. 2. Backup current configuration and data. 3. Install the updated version. 4. Restart the application service. 5. Verify functionality.
🔧 Temporary Workarounds
Implement server-side authorization
allAdd server-side permission validation to complement client-side checks
Network segmentation
allRestrict access to the application to authorized users only
🧯 If You Can't Patch
- Implement strict access controls and monitor for unusual privilege escalation attempts
- Deploy application-level firewalls to detect and block unauthorized privilege changes
🔍 How to Verify
Check if Vulnerable:
Check the application version in the admin interface or configuration files for version 4.2.0.4Check Version:
Check application settings or configuration files for version informationVerify Fix Applied:
Verify the application version is 4.2.0.5 or later and test privilege escalation attempts📡 Detection & Monitoring
Log Indicators:
- Unusual privilege changes
- Access to restricted functions by non-admin users
- Failed authorization attempts
Network Indicators:
- Unexpected API calls to privilege-related endpoints
- Traffic patterns indicating privilege escalation attempts
SIEM Query:
source="zauner_arc" AND (event="privilege_change" OR event="unauthorized_access")