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Virsec Security Research Lab

CVE-2020-26278: Weave Net/ Docker - Command Injection

Virsec Security Research Lab Vulnerability Analysis

The Virsec Security Research Lab provides timely, relevant analysis about recent and notable security vulnerabilities.

1.1        Vulnerability Summary

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.

cve-2020-26278

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1.2        CVSS Score

NVD Base score of this vulnerability is Not Available, but as per GitHub, score is 5.8 Medium . CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:C/C:N/I:H/A:N

1.3        Affected Version

Weave Net before version 2.8.0

1.4        Vulnerability Attribution

This vulnerability is reported by GitHub, Inc

1.5        Risk Impact

Weave Net provides a network to connect all pods together, implementing the Kubernetes model. Kubernetes uses the Container Network Interface (CNI) to join pods onto Weave Net.

Kubernetes implements many network features itself on top of the pod network. This includes ServicesService Discovery via DNS and Ingress into the cluster

Exploiting this vulnerability will allow an attacker to take over any host in the cluster and can also be used to can be used to escalate other Kubernetes vulnerabilities. There are no publicly available exploits.

1.6        Virsec Security Platform (VSP) Support:

VSP-Web capability can detect all types of command injection attack and prevent this attack from being exploited.

1.7        Reference Links:


 

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