CVE-2021-45893
📋 TL;DR
Softwarebuero Zauner ARC 4.2.0.4 has improper case sensitivity handling in password authentication, making brute-force attacks more effective by reducing the password search space. This affects organizations using this specific version of the ARC software for authentication. Attackers can more easily guess passwords since uppercase/lowercase variations aren't properly distinguished.
💻 Affected Systems
- Softwarebuero Zauner ARC
📦 What is this software?
Arc by Zauner
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise through successful password guessing leading to unauthorized access to sensitive systems and data.
Likely Case
Unauthorized access to user accounts through brute-force attacks, potentially leading to data exposure or privilege escalation.
If Mitigated
Limited impact with strong password policies, account lockouts, and network segmentation in place.
🎯 Exploit Status
Exploitation requires access to authentication interface. The vulnerability simplifies brute-force attacks but doesn't bypass authentication entirely.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.2.0.5 or later
Vendor Advisory: https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2021-065.txt
Restart Required: Yes
Instructions:
1. Download latest version from vendor. 2. Backup current installation. 3. Install update following vendor instructions. 4. Restart ARC services. 5. Verify authentication works correctly.
🔧 Temporary Workarounds
Implement account lockout policy
allConfigure account lockout after failed login attempts to mitigate brute-force attacks
Configure in ARC administration console: Set account lockout threshold to 5-10 failed attempts
Enforce complex passwords
allRequire passwords with mixed case, numbers, and special characters to compensate for case sensitivity weakness
Set minimum password length to 12+ characters
Require at least 3 character types (uppercase, lowercase, numbers, symbols)
🧯 If You Can't Patch
- Implement network segmentation to restrict access to ARC authentication interface
- Enable detailed authentication logging and monitor for brute-force patterns
🔍 How to Verify
Check if Vulnerable:
Check ARC version in administration console or about dialog. If version is exactly 4.2.0.4, system is vulnerable.Check Version:
Check ARC administration interface or run vendor-provided version check utilityVerify Fix Applied:
After update, verify version shows 4.2.0.5 or later. Test authentication with case-sensitive passwords.📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts from single source
- Successful logins after many failures
- Authentication logs showing case-insensitive password matching
Network Indicators:
- High volume of authentication requests to ARC port
- Pattern of incremental password attempts
SIEM Query:
source="ARC" AND (event_type="auth_failure" count>10 within 5min) OR (event_type="auth_success" AFTER multiple failures)