CVE-2020-10749: CNI Network Plugins MitM Vulnerability

CVE-2020-10749 Overview

A vulnerability was discovered in containernetworking/plugins before version 0.8.6 that enables malicious containers in Kubernetes clusters to perform man-in-the-middle (MitM) attacks. This flaw allows a malicious container to send rogue IPv6 router advertisements to the host or other containers, effectively redirecting network traffic to the attacker-controlled container.

Critical Impact

Malicious containers can intercept and manipulate network traffic within Kubernetes clusters by exploiting IPv6 router advertisement mechanisms, potentially compromising confidentiality and integrity of inter-container communications.

Affected Products

• Linux Foundation CNI Network Plugins (all versions before 0.8.6)
• Red Hat OpenShift Container Platform 4.0
• Fedora 32
• Red Hat Enterprise Linux 7.0 and 8.0

Discovery Timeline

• June 3, 2020 - CVE-2020-10749 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-10749

Vulnerability Analysis

This vulnerability exists within the Container Network Interface (CNI) plugins used extensively in Kubernetes and container orchestration environments. The flaw stems from improper handling of IPv6 Router Advertisements (RAs) within the container network stack. When containers are deployed with IPv6 networking enabled, the CNI plugins fail to adequately filter or validate incoming router advertisements.

The vulnerability allows an attacker who has already compromised or deployed a malicious container within the same Kubernetes cluster to broadcast rogue IPv6 router advertisements. These advertisements can manipulate the IPv6 routing tables of neighboring containers and potentially the host system itself, causing legitimate traffic to be redirected through the attacker's container.

Root Cause

The root cause of CVE-2020-10749 is insufficient network isolation and lack of proper filtering for IPv6 Router Advertisement packets within the CNI network plugins. The container networking stack does not implement adequate controls to prevent containers from sending or receiving arbitrary RA packets, which are typically trusted in IPv6 networks for automatic address configuration and routing.

The absence of RA filtering at the container network boundary allows any container to act as an IPv6 router, violating the principle of least privilege and enabling network-based attacks between containers that should otherwise be isolated.

Attack Vector

The attack requires network access and low privileges, specifically requiring the attacker to already have a foothold within the Kubernetes cluster (e.g., through a compromised or malicious container). The attack chain involves:

1. Deploying or compromising a container within the target Kubernetes cluster
2. Crafting and broadcasting malicious IPv6 Router Advertisement packets
3. Poisoning the IPv6 routing tables of victim containers or hosts
4. Intercepting redirected traffic for man-in-the-middle attacks

The attack exploits the trusted nature of IPv6 Router Advertisements in autoconfiguration scenarios, where systems automatically accept routing information from RA packets to configure their network interfaces.

Detection Methods for CVE-2020-10749

Indicators of Compromise

• Unexpected IPv6 Router Advertisement packets originating from container IP addresses
• Sudden changes in IPv6 routing tables on container hosts or within containers
• Unusual network traffic patterns showing traffic redirection through unexpected intermediate containers
• Multiple containers advertising themselves as IPv6 routers when they should not have routing capabilities

Detection Strategies

• Monitor for IPv6 RA packets within container networks using network traffic analysis tools
• Implement logging for IPv6 routing table changes on Kubernetes nodes and within containers
• Deploy network security monitoring to detect anomalous east-west traffic patterns within clusters
• Use container runtime security tools to detect containers sending ICMP Router Advertisement messages

Monitoring Recommendations

• Enable enhanced network logging on Kubernetes nodes to capture IPv6-related events
• Implement network policy monitoring to detect traffic flows that violate expected container communication patterns
• Deploy runtime security solutions that can alert on suspicious network activity within container environments
• Regularly audit container network configurations and CNI plugin versions across the cluster

How to Mitigate CVE-2020-10749

Immediate Actions Required

• Upgrade containernetworking/plugins to version 0.8.6 or later immediately
• Review and update Red Hat OpenShift Container Platform, Fedora, and RHEL installations with applicable security patches
• Disable IPv6 in container networks if not required for operations
• Implement network policies to restrict inter-container communication to only what is necessary

Patch Information

The vulnerability has been addressed in containernetworking/plugins version 0.8.6. Security patches have been released by multiple vendors including Red Hat, Fedora, and openSUSE. For detailed patch information, refer to the Red Hat Bug Report for CVE-2020-10749, Fedora Package Announcement, and the Kubernetes Security Announcement.

Workarounds

• Disable IPv6 on container network interfaces if IPv6 functionality is not required in your environment
• Implement strict network policies using Kubernetes NetworkPolicy resources to limit container-to-container communication
• Deploy host-level firewall rules to filter IPv6 Router Advertisement packets from container network interfaces
• Consider using network plugins that provide built-in RA filtering capabilities until patching is complete

# Disable IPv6 in container runtime (example for Docker)
# Add to /etc/docker/daemon.json
{
  "ipv6": false,
  "fixed-cidr-v6": ""
}

# Alternatively, disable IPv6 at the kernel level for container namespaces
sysctl -w net.ipv6.conf.all.disable_ipv6=1
sysctl -w net.ipv6.conf.default.disable_ipv6=1