8.8 High
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
6.5 Medium
CVSS2
Access Vector
NETWORK
Access Complexity
LOW
Authentication
SINGLE
Confidentiality Impact
PARTIAL
Integrity Impact
PARTIAL
Availability Impact
PARTIAL
AV:N/AC:L/Au:S/C:P/I:P/A:P
0.001 Low
EPSS
Percentile
31.4%
An issue was discovered in Rancher where an authorization logic flaw allows an authenticated user on any downstream cluster to (1) open a shell pod in the Rancher local
cluster and (2) have limited kubectl
access to it. The expected behavior is that a user does not have such access in the Rancher local
cluster unless explicitly granted.
This issue does not allow the user to escalate privileges in the local
cluster directly (this would require another vulnerability to be exploited).
The security issue happens in two different ways:
Shell pod access - This is when a user opens a shell pod in the Rancher UI to a downstream cluster that the user has permission to access. The web request can be intercepted using the browser’s web inspector/network console or a proxy tool to change the shell’s destination to the Rancher local
cluster instead of the desired downstream cluster.
This flaw cannot be exploited to access a downstream cluster that the user has no permissions to.
The shell pod runs with a limited non-root user, reducing the severity of this issue. However, even as a non-root user, it is still possible download and run binaries inside the shell pod.
The blast radius of this issue can increase based on the configuration of the local
cluster. For example:
If the local
cluster has unlimited network access, e.g. to the Internet, the user can open a reverse network connection to the shell pod.
Or access the cloud metadata API of the underlying cloud infrastructure, where the user can extract the credentials associated with the local
cluster and use them to interact with the cloud environment (this will be limited by the permissions granted to the cloud credentials in question).
Check further recommendations about liming access to the cloud metadata API in Rancher’s security best practices.
Kubectl access - When downloading the kubeconfig file of a downstream cluster that the user has access to, the server
cluster address in the kubeconfig file can be changed to point to the Rancher local
cluster instead of the intended downstream cluster.
This can also be achieved by crafting a kubeconfig using a Rancher token instead of using the kubeconfig from an active cluster.
This flaw cannot be exploited to access a downstream cluster that the user has no permissions to.
Notes:
local
cluster means the cluster where Rancher is installed. It is named as local
inside the list of clusters in the Rancher UI.1
or above.There is no workaround or direct mitigation besides updating to a patched Rancher version.
Patched versions include releases 2.5.17, 2.6.10, 2.7.1 and later versions.
If you have any questions or comments about this advisory:
CPE | Name | Operator | Version |
---|---|---|---|
github.com/rancher/rancher | lt | 2.7.1 | |
github.com/rancher/rancher | lt | 2.6.10 | |
github.com/rancher/rancher | lt | 2.5.17 |
8.8 High
CVSS3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
6.5 Medium
CVSS2
Access Vector
NETWORK
Access Complexity
LOW
Authentication
SINGLE
Confidentiality Impact
PARTIAL
Integrity Impact
PARTIAL
Availability Impact
PARTIAL
AV:N/AC:L/Au:S/C:P/I:P/A:P
0.001 Low
EPSS
Percentile
31.4%