CVE-2025-23018
📋 TL;DR
This vulnerability allows attackers to spoof and route arbitrary network traffic through systems with IPv4-in-IPv6 or IPv6-in-IPv6 tunneling enabled, bypassing source validation. It affects any system implementing RFC 2473 tunneling protocols without proper source verification. Network administrators and organizations using IPv6 tunneling are primarily affected.
💻 Affected Systems
- Any system implementing RFC 2473 IPv6 tunneling
📦 What is this software?
Ipv6 by Ietf
⚠️ Risk & Real-World Impact
Worst Case
Attackers could route malicious traffic through vulnerable systems to conduct DDoS attacks, exfiltrate data, or pivot to internal networks while hiding their true source.
Likely Case
Traffic spoofing allowing attackers to bypass network filtering, conduct reconnaissance, or perform man-in-the-middle attacks on tunneled traffic.
If Mitigated
Limited impact with proper network segmentation, egress filtering, and disabled unnecessary tunneling interfaces.
🎯 Exploit Status
Similar to CVE-2020-10136 exploitation patterns. Attack requires network access to vulnerable tunneling interface.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not applicable - protocol-level issue
Vendor Advisory: https://www.kb.cert.org/vuls/id/199397
Restart Required: No
Instructions:
1. Monitor vendor advisories for implementation-specific fixes
2. Apply workarounds until protocol updates available
3. Consider disabling unnecessary tunneling interfaces
🔧 Temporary Workarounds
Disable IPv6 Tunneling Interfaces
linuxRemove or disable unused IPv6 tunneling interfaces to eliminate attack surface
ip tunnel del <tunnel_name>
ifconfig <tunnel_interface> down
Implement Egress Filtering
linuxFilter outbound traffic from tunneling interfaces to prevent traffic routing
iptables -A OUTPUT -o tun6to4 -j DROP
iptables -A OUTPUT -o sit+ -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation to isolate tunneling interfaces
- Deploy network monitoring and IDS/IPS to detect spoofed tunneling traffic
🔍 How to Verify
Check if Vulnerable:
Check for active IPv6 tunneling interfaces: 'ip tunnel show' or 'ifconfig -a | grep -E "(tun|sit|ip6tnl)"'Check Version:
Not applicable - check system configuration instead of versionVerify Fix Applied:
Verify tunneling interfaces are disabled: 'ip tunnel show' should show no active tunnels📡 Detection & Monitoring
Log Indicators:
- Unexpected traffic spikes on tunneling interfaces
- Suspicious source addresses in tunneled packets
Network Indicators:
- Unusual traffic patterns through tunneling interfaces
- Spoofed source addresses in IPv6 tunnel headers
SIEM Query:
source_ip=* AND (interface="tun*" OR interface="sit*") AND bytes_sent > threshold