RHSA-2026:66350 - Security Advisory

Topic

Red Hat OpenShift Container Platform release 4.21.33 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 RPM packages for Red Hat OpenShift Container
Platform 4.21.33. See the following advisory for the container images for
this release:

https://access.redhat.com/errata/RHSA-2026:66352

Security Fix(es):

• net/http/internal/http2: golang: golang.org/x/net: Go HTTP/2: Denial of

Service via malformed SETTINGS_MAX_FRAME_SIZE frame (CVE-2026-33814)

• encoding/asn1: golang: Go encoding/asn1: Denial of Service via excessive

recursion in Unmarshal (CVE-2026-33818)

• golang.org/x/net/idna: golang: net/http: golang.org/x/net/idna: Privilege

escalation via incorrect Punycode label processing (CVE-2026-39821)

• golang: Go os.Root: Symlink following vulnerability allows directory

traversal (CVE-2026-39822)

• mime: golang: Golang MIME: Denial of Service via maliciously-crafted MIME

header (CVE-2026-42504)

• encoding/xml: golang: Go: Denial of Service via XML decoding recursion

depth issue (CVE-2026-56859)

• net/url: golang: golang net/url: Denial of Service from quadratic

complexity in path resolution (CVE-2026-56860)

• crypto/tls: golang: Golang crypto/tls: Denial of Service via indefinite

KeyUpdate messages (CVE-2026-56862)

For more details about the security issue(s), including the impact, a CVSS
score, acknowledgments, and other related information, refer to the CVE
page(s) listed in the References section.

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.

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/

Affected Products

• Red Hat OpenShift Container Platform 4.21 for RHEL 9 x86_64
• Red Hat OpenShift Container Platform 4.21 for RHEL 8 x86_64
• Red Hat OpenShift Container Platform for Power 4.21 for RHEL 9 ppc64le
• Red Hat OpenShift Container Platform for Power 4.21 for RHEL 8 ppc64le
• Red Hat OpenShift Container Platform for IBM Z and LinuxONE 4.21 for RHEL 9 s390x
• Red Hat OpenShift Container Platform for IBM Z and LinuxONE 4.21 for RHEL 8 s390x
• Red Hat OpenShift Container Platform for ARM 64 4.21 for RHEL 9 aarch64
• Red Hat OpenShift Container Platform for ARM 64 4.21 for RHEL 8 aarch64

Fixes

• BZ - 2467815 - CVE-2026-33814 net/http/internal/http2: golang: golang.org/x/net: Go HTTP/2: Denial of Service via malformed SETTINGS_MAX_FRAME_SIZE frame
• BZ - 2480756 - CVE-2026-39821 golang.org/x/net/idna: golang: net/http: golang.org/x/net/idna: Privilege escalation via incorrect Punycode label processing
• BZ - 2484204 - CVE-2026-42504 mime: golang: Golang MIME: Denial of Service via maliciously-crafted MIME header
• BZ - 2498152 - CVE-2026-39822 golang: Go os.Root: Symlink following vulnerability allows directory traversal
• BZ - 2515815 - CVE-2026-33818 encoding/asn1: golang: Go encoding/asn1: Denial of Service via excessive recursion in Unmarshal
• BZ - 2515820 - CVE-2026-56860 net/url: golang: golang net/url: Denial of Service from quadratic complexity in path resolution
• BZ - 2515839 - CVE-2026-56862 crypto/tls: golang: Golang crypto/tls: Denial of Service via indefinite KeyUpdate messages
• BZ - 2515840 - CVE-2026-56859 encoding/xml: golang: Go: Denial of Service via XML decoding recursion depth issue

CVEs

• CVE-2026-33814
• CVE-2026-33818
• CVE-2026-39821
• CVE-2026-39822
• CVE-2026-42504
• CVE-2026-56859
• CVE-2026-56860
• CVE-2026-56862

References

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