A security issue was discovered in Kubernetes where a user may be able to create a container with subpath volume mounts to access files & directories outside of the volume, including on the host filesystem.
A security issue was discovered in Kubernetes where a user may be able to create a container with subpath volume mounts to access files & directories outside of the volume, including on the host filesystem.

This issue has been rated **High** ([CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H](https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)), and assigned **CVE-2021-25741**.

### Affected Components and Configurations
This bug affects kubelet.


Environments where cluster administrators have restricted the ability to create hostPath mounts are the most seriously affected. Exploitation allows hostPath-like access without use of the hostPath feature, thus bypassing the restriction. 


In a default Kubernetes environment, exploitation could be used to obscure misuse of already-granted privileges.

#### Affected Versions
v1.22.0 - v1.22.1

v1.21.0 - v1.21.4

v1.20.0 - v1.20.10

<= v1.19.14

#### Fixed Versions
This issue is fixed in the following versions:

v1.22.2

v1.21.5

v1.20.11

v1.19.15

### Mitigation
To mitigate this vulnerability without upgrading kubelet, you can disable the VolumeSubpath feature gate on kubelet and kube-apiserver, and remove any existing Pods making use of the feature.


You can also use admission control to prevent less-trusted users from running containers as root to reduce the impact of successful exploitation.

### Detection
If you find evidence that this vulnerability has been exploited, please contact security@kubernetes.io

### Additional Details
See Kubernetes Issue #104980 for more details.

### Acknowledgements
This vulnerability was reported by Fabricio Voznika and Mark Wolters of Google.


Thanks as well to Ian Coldwater, Duffie Cooley, Brad Geesaman, and Rory McCune for the thorough security research that led to the discovery of this vulnerability.
CVE-2021-25741: Symlink Exchange Can Allow Host Filesystem Access
This is a GitHub Issue
repo:kubernetes
owner:kubernetes
Title : CVE-2021-25741: Symlink Exchange Can Allow Host Filesystem Access
Issue date:

--- start body ---
A security issue was discovered in Kubernetes where a user may be able to create a container with subpath volume mounts to access files & directories outside of the volume, including on the host filesystem.

This issue has been rated **High** ([CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H](https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)), and assigned **CVE-2021-25741**.

### Affected Components and Configurations
This bug affects kubelet.


Environments where cluster administrators have restricted the ability to create hostPath mounts are the most seriously affected. Exploitation allows hostPath-like access without use of the hostPath feature, thus bypassing the restriction. 


In a default Kubernetes environment, exploitation could be used to obscure misuse of already-granted privileges.

#### Affected Versions
v1.22.0 - v1.22.1

v1.21.0 - v1.21.4

v1.20.0 - v1.20.10

<= v1.19.14

#### Fixed Versions
This issue is fixed in the following versions:

v1.22.2

v1.21.5

v1.20.11

v1.19.15

### Mitigation
To mitigate this vulnerability without upgrading kubelet, you can disable the VolumeSubpath feature gate on kubelet and kube-apiserver, and remove any existing Pods making use of the feature.


You can also use admission control to prevent less-trusted users from running containers as root to reduce the impact of successful exploitation.

### Detection
If you find evidence that this vulnerability has been exploited, please contact security@kubernetes.io

### Additional Details
See Kubernetes Issue #104980 for more details.

### Acknowledgements
This vulnerability was reported by Fabricio Voznika and Mark Wolters of Google.


Thanks as well to Ian Coldwater, Duffie Cooley, Brad Geesaman, and Rory McCune for the thorough security research that led to the discovery of this vulnerability.
--- end body ---

CVE-2021-25741 is a security vulnerability in Kubernetes that allows users to create containers with subpath volume mounts, potentially granting access to files and directories outside of the intended volume, including the host filesystem. This can lead to unauthorized access to sensitive data and is rated as High severity. The issue affects kubelet and specific versions of Kubernetes, and it can be mitigated by disabling the VolumeSubpath feature gate or using admission control to restrict container privileges.