RHSA-2026:25186CriticalCVSS 8.8

Red Hat Security Advisory: OpenShift Container Platform 4.21.20 bug fix and security update

Published
June 16, 2026
Last Modified
August 21, 2026

🔗 CVE IDs covered (1)

CVE-2026-43037 →

📋 Description

CVE-2026-43037 — kernel: ip6_tunnel: clear skb2->cb[] in ip4ip6_err()

🎯 Affected products5

  • Red Hat OpenShift Container Platform 4.21
  • rhcos-aarch64-4.21.9.6.202606101139-0 as a component of Red Hat OpenShift Container Platform 4.21
  • rhcos-ppc64le-4.21.9.6.202606101139-0 as a component of Red Hat OpenShift Container Platform 4.21
  • rhcos-s390x-4.21.9.6.202606101139-0 as a component of Red Hat OpenShift Container Platform 4.21
  • rhcos-x86_64-4.21.9.6.202606101139-0 as a component of Red Hat OpenShift Container Platform 4.21

✅ Remediation

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: https://art-dash.engineering.redhat.com/ (For x86_64 architecture) The image digest is sha256:e2f30027fa1240272c8a472d6c77218ebc486bb966b6862c121187801a40163b (For s390x architecture) The image digest is sha256:84aafe31c3f70600df9b6466f6d1f758701c46ef306105af008964478a8e1431 (For ppc64le architecture) The image digest is sha256:4ec235e09584bc41d185f7e16405d978ec943670de859260fde0ba150fc12fb0 (For aarch64 architecture) The image digest is sha256:37b527aab81b3151268ea260005b088a7814bfbf55dd0e00cc1c23993bb14eaa 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. Workaround: Mitigation for this issue is to skip loading the affected module `ip6_tunnel` onto the system till we have a fix available, this can be done by a blacklist mechanism, this will ensure the driver is not loaded at the boot time. ~~~ How do I blacklist a kernel module to prevent it from loading automatically? https://access.redhat.com/solutions/41278 ~~~ We may also want to detection and monitoring an affected system as below: ~~~ Monitor for exploitation attempts: # Enable kernel audit for IPv6 tunnel operations auditctl -a always,exit -F arch=b64 -S socket -F a0=10 -F a1=3 -k ipv6_tunnel # Monitor system logs for kernel panics/crashes journalctl -k -p err -f | grep -i "ip6_tunnel\|icmp\|stack" ~~~

🔗 References (5)