CVE-2021-3636
Description
It was found in OpenShift, before version 4.8, that the generated certificate for the in-cluster Service CA, incorrectly included additional certificates. The Service CA is automatically mounted into all pods, allowing them to safely connect to trusted in-cluster services that present certificates signed by the trusted Service CA. The incorrect inclusion of additional CAs in this certificate would allow an attacker that compromises any of the additional CAs to masquerade as a trusted in-cluster service.
Statement
Though this CVE is fixed by default in freshly installed OpenShift 4.8 clusters, existing clusters that upgrade to 4.8 will need to opt-in to the new secure behaviour. Once opted-in, it is not possible to revert to the previous insecure behaviour.
Clusters can opt-in to the new secure behaviour by upgrading to version 4.8 or later and then setting "spec.useMoreSecureServiceCA" to true in the KubeControllerManager API object, e.g.:
$ oc patch KubeControllerManager cluster -p '{"spec": {"useMoreSecureServiceCA": true}}' --type=merge
The kube-controller-manager pod will then restart before the changes to take effect. New pods will then be provisioned with the secure Service CA.
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 | 4.6 | 4.6 | N/A |
| Attack Vector | Adjacent Network | Adjacent Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | Low | Low | N/A |
| Integrity Impact | Low | Low | N/A |
| Availability Impact | None | None | N/A |
Vector
Red Hat: CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
NVD: CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Understanding the Weakness (CWE)
Integrity,Authentication
Technical Impact: Bypass Protection Mechanism; Gain Privileges or Assume Identity
When a certificate is invalid or malicious, it might allow an attacker to spoof a trusted entity by interfering in the communication path between the host and client. The product might connect to a malicious host while believing it is a trusted host, or the product might be deceived into accepting spoofed data that appears to originate from a trusted host.
Frequently Asked Questions
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