CVE-2020-1749
📋 TL;DR
This vulnerability in the Linux kernel causes IPsec-encrypted VXLAN and GENEVE tunnels over IPv6 to send data unencrypted instead of through the encrypted link. Anyone between the tunnel endpoints can read the traffic, compromising data confidentiality. Systems using these specific tunnel configurations with IPv6 are affected.
💻 Affected Systems
- Linux kernel
📦 What is this software?
Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →⚠️ Risk & Real-World Impact
Worst Case
All traffic through affected tunnels is exposed in plaintext to network eavesdroppers, potentially revealing sensitive data including credentials, business information, and personal data.
Likely Case
Partial traffic exposure where some encrypted tunnel sessions fail to encrypt properly, leading to intermittent data leakage.
If Mitigated
No data exposure if proper network segmentation and monitoring prevent unauthorized access to the network path between tunnel endpoints.
🎯 Exploit Status
Exploitation requires network access between tunnel endpoints but no authentication. The flaw is in the routing logic, so exploitation is passive eavesdropping rather than active attack.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Varies by distribution - check vendor advisories
Vendor Advisory: https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2020-1749
Restart Required: Yes
Instructions:
1. Check your Linux distribution's security advisories. 2. Update kernel package to patched version. 3. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable affected tunnel configurations
linuxTemporarily disable VXLAN and GENEVE tunnels over IPv6 with IPsec until patching is complete
# Disable specific tunnel interfaces
# ip link delete vxlan0
# ip link delete geneve0
Use alternative encryption methods
linuxConfigure tunnels to use different encryption methods or tunnel types not affected by this vulnerability
🧯 If You Can't Patch
- Implement strict network segmentation to limit who can access traffic between tunnel endpoints
- Deploy network monitoring and intrusion detection to alert on unexpected plaintext traffic in tunnel paths
🔍 How to Verify
Check if Vulnerable:
Check kernel version and verify if VXLAN/GENEVE over IPv6 with IPsec is configured: # uname -r and # ip -d link showCheck Version:
uname -rVerify Fix Applied:
Verify kernel version is updated to patched version and test tunnel encryption with packet capture tools📡 Detection & Monitoring
Log Indicators:
- Kernel logs showing tunnel establishment
- IPsec negotiation failures
Network Indicators:
- Plaintext traffic observed between tunnel endpoints where encryption was expected
- Unexpected protocol patterns in tunnel traffic
SIEM Query:
Search for network traffic patterns showing unencrypted data between known tunnel endpoints