CVE-2024-7595
📋 TL;DR
This vulnerability allows attackers to spoof GRE/GRE6 protocol packets by bypassing source validation, enabling them to route arbitrary traffic through exposed network interfaces. This affects any system using GRE/GRE6 tunneling protocols without proper source validation controls. Network devices, routers, and systems with GRE interfaces are primarily impacted.
💻 Affected Systems
- Network devices with GRE/GRE6 support
- Routers with GRE tunneling
- Systems using GRE for VPNs
- Any implementation of RFC2784
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete network compromise through traffic redirection, data interception, access control bypass, and potential lateral movement across network segments.
Likely Case
Network spoofing attacks, unauthorized traffic routing, potential data leakage, and disruption of legitimate GRE tunnel communications.
If Mitigated
Limited impact with proper network segmentation, firewall rules, and source validation controls in place.
🎯 Exploit Status
Similar to CVE-2020-10136, exploitation requires network access to GRE interfaces but is technically straightforward once access is obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: N/A
Vendor Advisory: N/A
Restart Required: No
Instructions:
No official patch exists as this is a protocol-level issue. Implement workarounds and monitor vendor-specific mitigations.
🔧 Temporary Workarounds
Implement Source Validation
linuxConfigure network devices to validate GRE packet sources using ACLs or firewall rules
# Example: iptables rule for Linux
# iptables -A INPUT -p gre -m state --state NEW -j DROP
# iptables -A INPUT -p gre -s trusted_source -m state --state NEW -j ACCEPT
Disable Unnecessary GRE Interfaces
linuxTurn off GRE interfaces not required for operations
# Linux: ip tunnel del gre0
# Check existing tunnels: ip tunnel show
🧯 If You Can't Patch
- Implement strict network segmentation to isolate GRE traffic
- Deploy network monitoring and IDS/IPS systems to detect GRE spoofing attempts
🔍 How to Verify
Check if Vulnerable:
Check if GRE interfaces are active and exposed: On Linux: 'ip tunnel show' or 'ifconfig -a | grep gre'. Check firewall rules for GRE protocol filtering.Check Version:
Protocol-level vulnerability - check GRE implementation status rather than specific versionsVerify Fix Applied:
Verify GRE interfaces are either disabled or have proper source validation rules. Test with controlled spoofing attempts.📡 Detection & Monitoring
Log Indicators:
- Unexpected GRE tunnel establishment
- GRE packets from unauthorized sources
- Network traffic anomalies through GRE interfaces
Network Indicators:
- GRE packets with spoofed source addresses
- Unusual traffic patterns through GRE tunnels
- Protocol 47 (GRE) traffic from unexpected sources
SIEM Query:
Example: (protocol:47 AND (src_ip NOT IN allowed_gre_sources)) OR (gre_tunnel_establishment FROM unexpected_ip)