CVE-2020-14336
Description
A flaw was found in the Restricted Security Context Constraints (SCC), where it allows pods to craft custom network packets. This flaw allows an attacker to cause a denial of service attack on an OpenShift Container Platform cluster if they can deploy pods. The highest threat from this vulnerability is to system availability.
Statement
By default, the OpenShift Container Platform uses the OpenShift SDN network interface. This interface makes this attack impractical by implementing IPTable rules on the host side of the virtual network interface, isolating network traffic to within the pod.
If the OpenShift Container Platform has the sriov-network-operator deployed, it is at a greater risk for exploitation.
If installing a new OCP 4.6 cluster no changes are required. If upgrading a cluster from an earlier version to 4.5.16 be sure to delete 99-worker-generated-crio-capabilities and 99-master-generated-crio-capabilities machine controllers once you have tested that dropping NET_RAW does not break your cluster workload.
Mitigation
On OCP 3.11 create a custom SCC based on 'restricted' and also drop the NET_RAW capability[1]. Assign this custom SCC to any users, or groups which create pods you want to protect. See the documentation for more information [2].
[1] https://access.redhat.com/solutions/5611521
[2] https://docs.openshift.com/container-platform/3.11/admin_guide/manage_scc.html
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).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 3.1 | 6.5 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | High | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | Low | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
NVD: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
When allocating resources without limits, an attacker could prevent other systems, applications, or processes from accessing the same type of resource. It can be easy for an attacker to consume many resources by rapidly making many requests or causing larger resources to be used than is needed.
Acknowledgements
This issue was discovered by Yuval Kashtan (Red Hat).
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