Clusters using Calico (version 3.14.0 and below), Calico Enterprise (version 2.8.2 and below), may be vulnerable to information disclosure if IPv6 is enabled but unused. A compromised pod with sufficient privilege is able to reconfigure the node’s IPv6 interface due to the node accepting route advertisement by default, allowing the attacker to redirect full or partial network traffic from the node to the compromised pod.
CVSS Rating: [CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L](https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L) (6.0 Medium)

A cluster configured to use an affected container networking implementation is susceptible to man-in-the-middle (MitM) attacks. By sending “rogue” router advertisements, a malicious container can reconfigure the host to redirect part or all of the IPv6 traffic of the host to the attacker-controlled container. Even if there was no IPv6 traffic before, if the DNS returns A (IPv4) and AAAA (IPv6) records, many HTTP libraries will try to connect via IPv6 first then fallback to IPv4, giving an opportunity to the attacker to respond.

### Am I vulnerable?

Kubernetes itself is not vulnerable. A Kubernetes cluster using an affected networking implementation is vulnerable.

Binary releases of the kubelet installed from upstream Kubernetes Community repositories hosted at https://packages.cloud.google.com/ may have also installed the `kubernetes-cni` package containing the [containernetworking CNI plugins](https://github.com/containernetworking/plugins), which are affected by CVE-2020-10749.

#### Affected Versions
The following official kubelet package versions have an affected `kubernetes-cni` package as a dependency: 
- kubelet v1.18.0-v1.18.3
- kubelet v1.17.0-v1.17.6
- kubelet < v1.16.11

A cluster having an affected `kubernetes-cni` package installed is only affected if configured to use it.
#### Third-party components and versions
Many container networking implementations are affected, including:

- CNI Plugins maintained by the containernetworking team, prior to version 0.8.6 (CVE-2020-10749) (See https://github.com/containernetworking/plugins/pull/484)
- Calico and Calico Enterprise (CVE-2020-13597)  Please refer to the Tigera Advisory TTA-2020-001 at https://www.projectcalico.org/security-bulletins/ for details
- Docker versions prior to 19.03.11 (see https://github.com/docker/docker-ce/releases/v19.03.11) (CVE-2020-13401)
- Flannel, all current versions
- Weave Net, prior to version 2.6.3

It is believed that the following are not affected:

- Cilium
- Juniper Contrail Networking
- OpenShift SDN
- OVN-Kubernetes
- Tungsten Fabric

Information about the vulnerability status of any plugins or implementations not listed above is currently unavailable. Please contact the provider directly with questions about their implementation.

### How do I mitigate this vulnerability?
- Set the host default to reject router advertisements. This should prevent attacks from succeeding, but may break legitimate traffic, depending upon the networking implementation and the network where the cluster is running. To change this setting, set the sysctl `net.ipv6.conf.all.accept_ra` to 0.
- Use TLS with proper certificate validation
- Disallow `CAP_NET_RAW` for untrusted workloads or users. For example, a Pod Security Policy with a `RequiredDropCapabilities` that includes `NET_RAW` will prevent this attack for controlled workloads.

#### Fixed Versions

The following packages will bundle fixed versions of the containernetworking CNI plugins that were formerly installed via the `kubernetes-cni` package.
- kubelet v1.19.0+ (master branch #91370)
- kubelet v1.18.4+ (#91387)
- kubelet v1.17.7+ (#91386)
- kubelet v1.16.11+ (#91388)

Because these versions are not yet available, cluster administrators using packages from the Kubernetes repositories may choose to manually upgrade CNI plugins by retrieving the relevant arch tarball from the containernetworking/plugins [v0.8.6 release](https://github.com/containernetworking/plugins/releases/tag/v0.8.6). The patch versions are [expected to be released on June 17th](https://github.com/kubernetes/sig-release/blob/master/releases/patch-releases.md#timelines), subject to change.

## Additional Details
#### Detection

- The IPv6 routing table on nodes will show any attacker-created entries. For example, a host with IPv6 disabled might show no default route when running `ip -6 route` but the same host with an attack in progress might show an updated default route or a route to the target address(es). Any IPv6 route with a destination interface of a host-side container network interface should be investigated.
- The host-side of a container network interface may show additional configured IPv6 addresses after receiving a rogue RA packet. For example, given a host-side interface of `cbr0` which might normally have no IPv6 address, a dynamic-configured address on the interface may signal an attack in progress. Use this command to view interface addresses: `ip a show dynamic cbr0`

#### Affected configurations

- Clusters using an affected networking implementation and allowing workloads to run with `CAP_NET_RAW privileges`. The default Kubernetes security context runs workloads with a capabilities bounding set that includes `CAP_NET_RAW`. 

#### Vulnerability impact

- A user able to create containers with `CAP_NET_RAW` privileges on an affected cluster can intercept traffic from other containers on the host or from the host itself.

#### Acknowledgements

This vulnerability was reported by Etienne Champetier (@champtar).

The issue was fixed by Casey Callendrello (@squeed) and maintainers of various container networking implementations. Updates to Kubernetes builds were coordinated by Stephen Augustus (@justaugustus) and Tim Pepper (@tpepper).

/area security
/kind bug
/committee product-security
/sig network

CVE-2020-10749: IPv4 only clusters susceptible to MitM attacks via IPv6 rogue router advertisements
This is a GitHub Issue
repo:kubernetes
owner:kubernetes
Title : CVE-2020-10749: IPv4 only clusters susceptible to MitM attacks via IPv6 rogue router advertisements
Issue date:

--- start body ---
CVSS Rating: [CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L](https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:L) (6.0 Medium)

A cluster configured to use an affected container networking implementation is susceptible to man-in-the-middle (MitM) attacks. By sending “rogue” router advertisements, a malicious container can reconfigure the host to redirect part or all of the IPv6 traffic of the host to the attacker-controlled container. Even if there was no IPv6 traffic before, if the DNS returns A (IPv4) and AAAA (IPv6) records, many HTTP libraries will try to connect via IPv6 first then fallback to IPv4, giving an opportunity to the attacker to respond.

### Am I vulnerable?

Kubernetes itself is not vulnerable. A Kubernetes cluster using an affected networking implementation is vulnerable.

Binary releases of the kubelet installed from upstream Kubernetes Community repositories hosted at https://packages.cloud.google.com/ may have also installed the `kubernetes-cni` package containing the [containernetworking CNI plugins](https://github.com/containernetworking/plugins), which are affected by CVE-2020-10749.

#### Affected Versions
The following official kubelet package versions have an affected `kubernetes-cni` package as a dependency: 
- kubelet v1.18.0-v1.18.3
- kubelet v1.17.0-v1.17.6
- kubelet < v1.16.11

A cluster having an affected `kubernetes-cni` package installed is only affected if configured to use it.
#### Third-party components and versions
Many container networking implementations are affected, including:

- CNI Plugins maintained by the containernetworking team, prior to version 0.8.6 (CVE-2020-10749) (See https://github.com/containernetworking/plugins/pull/484)
- Calico and Calico Enterprise (CVE-2020-13597)  Please refer to the Tigera Advisory TTA-2020-001 at https://www.projectcalico.org/security-bulletins/ for details
- Docker versions prior to 19.03.11 (see https://github.com/docker/docker-ce/releases/v19.03.11) (CVE-2020-13401)
- Flannel, all current versions
- Weave Net, prior to version 2.6.3

It is believed that the following are not affected:

- Cilium
- Juniper Contrail Networking
- OpenShift SDN
- OVN-Kubernetes
- Tungsten Fabric

Information about the vulnerability status of any plugins or implementations not listed above is currently unavailable. Please contact the provider directly with questions about their implementation.

### How do I mitigate this vulnerability?
- Set the host default to reject router advertisements. This should prevent attacks from succeeding, but may break legitimate traffic, depending upon the networking implementation and the network where the cluster is running. To change this setting, set the sysctl `net.ipv6.conf.all.accept_ra` to 0.
- Use TLS with proper certificate validation
- Disallow `CAP_NET_RAW` for untrusted workloads or users. For example, a Pod Security Policy with a `RequiredDropCapabilities` that includes `NET_RAW` will prevent this attack for controlled workloads.

#### Fixed Versions

The following packages will bundle fixed versions of the containernetworking CNI plugins that were formerly installed via the `kubernetes-cni` package.
- kubelet v1.19.0+ (master branch #91370)
- kubelet v1.18.4+ (#91387)
- kubelet v1.17.7+ (#91386)
- kubelet v1.16.11+ (#91388)

Because these versions are not yet available, cluster administrators using packages from the Kubernetes repositories may choose to manually upgrade CNI plugins by retrieving the relevant arch tarball from the containernetworking/plugins [v0.8.6 release](https://github.com/containernetworking/plugins/releases/tag/v0.8.6). The patch versions are [expected to be released on June 17th](https://github.com/kubernetes/sig-release/blob/master/releases/patch-releases.md#timelines), subject to change.

## Additional Details
#### Detection

- The IPv6 routing table on nodes will show any attacker-created entries. For example, a host with IPv6 disabled might show no default route when running `ip -6 route` but the same host with an attack in progress might show an updated default route or a route to the target address(es). Any IPv6 route with a destination interface of a host-side container network interface should be investigated.
- The host-side of a container network interface may show additional configured IPv6 addresses after receiving a rogue RA packet. For example, given a host-side interface of `cbr0` which might normally have no IPv6 address, a dynamic-configured address on the interface may signal an attack in progress. Use this command to view interface addresses: `ip a show dynamic cbr0`

#### Affected configurations

- Clusters using an affected networking implementation and allowing workloads to run with `CAP_NET_RAW privileges`. The default Kubernetes security context runs workloads with a capabilities bounding set that includes `CAP_NET_RAW`. 

#### Vulnerability impact

- A user able to create containers with `CAP_NET_RAW` privileges on an affected cluster can intercept traffic from other containers on the host or from the host itself.

#### Acknowledgements

This vulnerability was reported by Etienne Champetier (@champtar).

The issue was fixed by Casey Callendrello (@squeed) and maintainers of various container networking implementations. Updates to Kubernetes builds were coordinated by Stephen Augustus (@justaugustus) and Tim Pepper (@tpepper).

/area security
/kind bug
/committee product-security
/sig network

--- end body ---

CVE-2020-10749 is a security vulnerability in Kubernetes that allows man-in-the-middle (MitM) attacks on IPv4-only clusters via rogue IPv6 router advertisements. This vulnerability can lead to traffic redirection to an attacker-controlled container, compromising the security of the cluster. The issue affects clusters using certain container networking implementations, particularly those with specific versions of the `kubernetes-cni` package. Mitigation strategies include rejecting router advertisements and using TLS with proper certificate validation.