CVE-2021-34575
📋 TL;DR
This vulnerability allows unauthenticated attackers to enumerate valid user accounts in MB connect line mymbCONNECT24 and mbCONNECT24 software. By analyzing server responses, attackers can determine which usernames exist in the system. Organizations using affected versions of these products are at risk.
💻 Affected Systems
- MB connect line mymbCONNECT24
- MB connect line mbCONNECT24
📦 What is this software?
Mbconnect24 by Mbconnectline
Mymbconnect24 by Mbconnectline
⚠️ Risk & Real-World Impact
Worst Case
Attackers could enumerate all valid users, then use credential stuffing or brute force attacks to gain unauthorized access to the system, potentially leading to data theft or system compromise.
Likely Case
Attackers will enumerate valid users to build targeted attack lists for credential stuffing or social engineering attacks against identified users.
If Mitigated
With proper network segmentation and monitoring, enumeration attempts can be detected and blocked before attackers can use the information for further attacks.
🎯 Exploit Status
The vulnerability is simple to exploit as it only requires analyzing server responses to authentication attempts.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: > 2.8.0
Vendor Advisory: https://cert.vde.com/de-de/advisories/vde-2021-030
Restart Required: Yes
Instructions:
1. Download the latest version from MB connect line. 2. Backup current configuration. 3. Install the update following vendor instructions. 4. Restart the service/application.
🔧 Temporary Workarounds
Network Access Control
allRestrict access to the vulnerable interface to trusted IP addresses only
Web Application Firewall
allConfigure WAF rules to detect and block user enumeration patterns
🧯 If You Can't Patch
- Implement rate limiting on authentication endpoints to slow down enumeration attempts
- Monitor authentication logs for unusual patterns of failed login attempts
🔍 How to Verify
Check if Vulnerable:
Test authentication endpoint responses with valid and invalid usernames - if responses differ, system is vulnerableCheck Version:
Check software version in administration interface or configuration filesVerify Fix Applied:
After patching, test that authentication endpoint returns identical responses for valid and invalid usernames📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts with different usernames from same source
- Pattern of authentication requests with incremental usernames
Network Indicators:
- Unusual volume of authentication requests to the web interface
- Requests to authentication endpoints from unexpected sources
SIEM Query:
source_ip=* AND (event_type="authentication_failure" OR event_type="login_failed") COUNT BY source_ip, username WHERE count > threshold