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CVE-2020-26278

Weave Net Pods running in host PID namespace can be used to escalate other Kubernetes vulnerabilities

5.8 Medium

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.

Attack profile

How easy it is to exploit

Attack vector
Adjacent network
Complexity
High
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
High
Availability
None

Exploit likelihood

0.74%Down 0.3 points since Apr 14, 2021
90%50%10%1%

What each source reports

CVE List Score used 5.8

Weave Net Pods running in host PID namespace can be used to escalate other Kubernetes vulnerabilities

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.

Record
CVE-2020-26278
CVSS 3.1
5.8 MediumCVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:C/C:N/I:H/A:N
Weakness
CWE-250
Updated
2026-11-02
EUVDEUVD-2020-18852 5.8

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.

Record
EUVD-2020-18852
CVSS 3.1
5.8 MediumCVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:C/C:N/I:H/A:N
Updated
2026-11-03
NVD 5.8

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.

Record
CVE-2020-26278
CVSS 3.1
5.8 MediumCVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:C/C:N/I:H/A:N
CVSS 3.1
8.0 HighCVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
CVSS 2.0
7.9 HighAV:A/AC:M/Au:N/C:C/I:C/A:C
Weakness
CWE-250
Updated
2026-11-02
OSV 8.0

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.

Record
CVE-2020-26278
CVSS 3.1
8.0 HighCVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
Updated
2026-11-02

Affected products

History

History
RecordedChangedSources
aliasesEUVD
first indexedCVE List, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2020-26278 is a medium vulnerability (CVSS 5.8) in Weave, published January 20, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.74%, the 54th percentile. No source names a fixed version.

References

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