RHSA-2026:21709 - Security Advisory

Topic

Red Hat OpenShift Container Platform release 4.21.18 is now available with updates to packages and images that fix several bugs and add enhancements.

This release includes a security update for Red Hat OpenShift Container Platform 4.21.

Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Description

Red Hat OpenShift Container Platform is Red Hat's cloud computing Kubernetes application platform solution designed for on-premise or private cloud deployments.

This advisory contains the container images for Red Hat OpenShift Container Platform 4.21.18. See the following advisory for the RPM packages for this release:

https://access.redhat.com/errata/RHBA-2026:21707

Space precludes documenting all of the container images in this advisory. See the following Release Notes documentation, which will be updated shortly for this release, for details about these changes:

https://docs.redhat.com/en/documentation/openshift_container_platform/4.21/html/release_notes/

Solution

For OpenShift Container Platform 4.21 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this asynchronous errata update:

https://docs.redhat.com/en/documentation/openshift_container_platform/4.21/html/release_notes/

You may download the oc tool and use it to inspect release image metadata for x86_64, s390x, ppc64le, and aarch64 architectures. The image digests may be found at https://quay.io/repository/openshift-release-dev/ocp-release?tab=tags.

The sha values for the release are as follows:

(For x86_64 architecture)
The image digest is sha256:81071b95d587ae2bb8f1d651c0d537d408fc4c86a5d664c7be077edf8ca99603

(For s390x architecture)
The image digest is sha256:3f6187bdaac8dd225d87416237c2b61741d12eb56ae8042563e851247d39d448

(For ppc64le architecture)
The image digest is sha256:0cd31c10b0d84d415b4fe035cc9a7bcc88f195c85bbd55c1c058a87e8e469e1f

(For aarch64 architecture)
The image digest is sha256:400c31a6bf0042e625fadb528ad0fe0bfcb03aeb31893bee18f77a9b59139d1a

All OpenShift Container Platform 4.21 users are advised to upgrade to these updated packages and images when they are available in the appropriate release channel. To check for available updates, use the OpenShift CLI (oc) or web console. Instructions for upgrading a cluster are available at https://docs.redhat.com/en/documentation/openshift_container_platform/4.21/html-single/updating_clusters/index#updating-cluster-cli.

Affected Products

• Red Hat OpenShift Container Platform

Fixes

• BZ - 2441268
• BZ - 2449833
• BZ - 2455470
• OCPBUGS-85041 - Manual networking configuration via agent TUI does not get persisted
• OCPBUGS-86037 - rpm-ostree karg append failed, no key found
• OCPBUGS-86119 - [release-4.21] Add unit and e2e test coverage for cert rotation redeployment (OCPBUGS-82037 follow-up)
• OCPBUGS-86232 - Machine Config Daemon failed to apply cgroup v2 kargs
• OCPBUGS-86250 - Prometheus panics on nil pointer in (*tlsRoundTripper).RoundTrip
• OCPBUGS-86438 - [release 4.21] - [Below the sea UI] Operators section should not be displayed on review and installation progress pages when no operators are selected
• OCPBUGS-86439 - [release 4.21] - [Below the sea UI] Remove Arbiter button from "Encryption of installation disks"

CVEs

• CVE-2026-26996
• CVE-2026-33186
• CVE-2026-34986

References

• https://access.redhat.com/security/updates/classification/