CVE-2025-41760
📋 TL;DR
This vulnerability allows network traffic to bypass intended filtering rules when administrators configure an empty pass filter table in UBR systems. Administrators who rely on this configuration to block all traffic will inadvertently permit all traffic instead. This affects systems using UBR with empty filter table configurations.
💻 Affected Systems
- UBR (Universal Broadband Router)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete network security bypass allowing unrestricted inbound and outbound traffic, potentially enabling data exfiltration, malware propagation, or unauthorized access to internal systems.
Likely Case
Accidental misconfiguration leads to unintended network traffic allowance, creating security policy violations and potential compliance issues.
If Mitigated
Proper monitoring detects the configuration error, and traffic is controlled through other security layers like firewalls or network segmentation.
🎯 Exploit Status
Exploitation requires administrative access to misconfigure the filter. This is primarily a configuration logic flaw rather than a traditional exploit.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not specified
Vendor Advisory: https://www.mbs-solutions.de/mbs-2025-0001
Restart Required: No
Instructions:
1. Review vendor advisory for specific patching information. 2. Update UBR software to version that addresses this logic flaw. 3. Verify filter configurations after update.
🔧 Temporary Workarounds
Configure explicit deny rules
allInstead of relying on empty tables, configure explicit deny-all rules for traffic filtering
# Configure explicit deny rule instead of empty table
# Example: deny all traffic on specific interface
Implement multi-layer filtering
allUse additional firewall or network security controls to enforce traffic restrictions
# Configure secondary firewall rules
# Example: iptables -P INPUT DROP
🧯 If You Can't Patch
- Audit all UBR configurations to ensure no empty pass filter tables are in use
- Implement network monitoring to detect unexpected traffic patterns that indicate filter bypass
🔍 How to Verify
Check if Vulnerable:
Check UBR configuration for empty pass filter tables. Review filter rules to ensure they contain explicit deny entries rather than empty tables.Check Version:
Check UBR version via administrative interface or CLI command specific to the UBR platformVerify Fix Applied:
After configuration changes, test traffic filtering by attempting to send blocked traffic and verifying it is properly denied.📡 Detection & Monitoring
Log Indicators:
- Configuration changes creating empty filter tables
- Unexpected traffic allowance through filtered interfaces
Network Indicators:
- Traffic flowing through interfaces that should be blocked
- Increased network traffic on filtered segments
SIEM Query:
Search for configuration changes containing 'empty table' or 'pass filter' in UBR logs, combined with traffic pattern anomalies