CVE-2020-26278
Weave Net Pods running in host PID namespace can be used to escalate other Kubernetes vulnerabilities
In short
Weave Net pods in Kubernetes were running with unnecessary access to the host's process namespace (hostPID), which could allow an attacker who gains code execution inside the pod to take over the entire host. This is a dangerous permission that wasn't needed for the software to function.
Technical detail
CVE-2020-26278 exploits an unnecessary hostPID: true setting in Weave Net DaemonSet manifests, allowing an attacker with code execution inside the privileged pod to access and manipulate all host processes and the root filesystem. The vulnerability requires a secondary attack vector (e.g., another Kubernetes vulnerability or misconfiguration) to initially compromise the Weave Net pod; exploitation enables full host compromise due to combined privileged and hostPID capabilities.
Summary generated and translated by AI from the official description.
Weave Net is open source software which creates a virtual network that connects Docker containers across multiple hosts and enables their automatic discovery. Weave Net before version 2.8.0 has a vulnerability in which can allow an attacker to take over any host in the cluster. Weave Net is supplied with a manifest that runs pods on every node in a Kubernetes cluster, which are responsible for managing network connections for all other pods in the cluster. This requires a lot of power over the host, and the manifest sets `privileged: true`, which gives it that power. It also set `hostPID: true`, which gave it the ability to access all other processes on the host, and write anywhere in the root filesystem of the host. This setting was not necessary, and is being removed. You are only vulnerable if you have an additional vulnerability (e.g. a bug in Kubernetes) or misconfiguration that allows an attacker to run code inside the Weave Net pod, No such bug is known at the time of release, and there are no known instances of this being exploited. Weave Net 2.8.0 removes the hostPID setting and moves CNI plugin install to an init container. Users who do not update to 2.8.0 can edit the hostPID line in their existing DaemonSet manifest to say false instead of true, arrange some other way to install CNI plugins (e.g. Ansible) and remove those mounts from the DaemonSet manifest.
CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:C/C:N/I:H/A:N