CVE-2020-26278: Weave Net is open source software which creates a virtual network that connects Docker containers across multiple hosts and enables their automatic di...

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.

Metrics

CVSS 3.1

8/10

CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

EPSS Probability

0.74%

49.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-250

Affected Software

Vendor	Product	Versions
Weave	Weave	< 2.8.0

References

https://github.com/weaveworks/weave/blob/master/CHANGELOG.md#release-280Release Notes, Third Party Advisory
https://github.com/weaveworks/weave/commit/a0ac81b3b4cae6d0dcaf3732fd91cedefc89f720Patch, Third Party Advisory
https://github.com/weaveworks/weave/pull/3876Patch, Third Party Advisory
https://github.com/weaveworks/weave/security/advisories/GHSA-pg3p-v8c6-c6h3Third Party Advisory
https://github.com/weaveworks/weave/blob/master/CHANGELOG.md#release-280Release Notes, Third Party Advisory
https://github.com/weaveworks/weave/commit/a0ac81b3b4cae6d0dcaf3732fd91cedefc89f720Patch, Third Party Advisory
https://github.com/weaveworks/weave/pull/3876Patch, Third Party Advisory
https://github.com/weaveworks/weave/security/advisories/GHSA-pg3p-v8c6-c6h3Third Party Advisory

Timeline

Published: Jan 20, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-26278?

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.

How severe is CVE-2020-26278?

CVE-2020-26278 has a CVSS score of 8/10 (HIGH severity). The EPSS model estimates a 0.74% probability of exploitation in the next 30 days.

How do I fix CVE-2020-26278?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.