CVE-2020-35514
Description
An insecure modification flaw in the /etc/kubernetes/kubeconfig file was found in OpenShift. This flaw allows an attacker with access to a running container which mounts /etc/kubernetes or has local access to the node, to copy this kubeconfig file and attempt to add their own node to the OpenShift cluster. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.
Statement
The kubeconfig file on the node is that of the bootstrap certificate. This means that to successfully exploit this vulnerability, the kubeconfig file must be taken and used within the first 24 hours of creation as it is created with a short expiration time. Otherwise, attempting to use the credentials after this time will result in the following:
Failed while requesting a signed certificate from the master: cannot create certificate signing request: Unauthorized
Further, if taken, the certificate signing request (CSR) of the joining rogue OpenShift node is not automatically approved by default. The node still needs to be approved through the use of the commands oc get csr and oc adm certificate approve.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7 | 7 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | High | High | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Access Control
Technical Impact: Gain Privileges or Assume Identity
A user can access restricted functionality and/or sensitive information that may include administrative functionality and user accounts.
Acknowledgements
This issue was discovered by Juan Osorio Robles (Red Hat).
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