RHSA-2026:59562 - Security Advisory

Topic

An update for osbuild-composer is now available for Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions.

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

A service for building customized OS artifacts, such as VM images and OSTree commits, that uses osbuild under the hood. Besides building images for local usage, it can also upload images directly to cloud. It is compatible with composer-cli and cockpit-composer clients.

Security Fix(es):

• golang.org/x/net/idna: golang: net/http: golang.org/x/net/idna: Privilege escalation via incorrect Punycode label processing (CVE-2026-39821)
• golang.org/x/net/html: golang: golang.org/x/net/html: Cross-Site Scripting via HTML parsing bypass (CVE-2026-27136)
• golang.org/x/net/html: golang.org/x/net/html: Arbitrary code execution via Cross-Site Scripting (CVE-2026-25681)
• golang.org/x/net/html: golang: golang.org/x/net/html: Cross-Site Scripting via unexpected HTML tree rendering (CVE-2026-42502)

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.

Solution

For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

Affected Products

• Red Hat Enterprise Linux Server - AUS 9.4 x86_64
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 9.4 ppc64le
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 9.4 x86_64
• Red Hat Enterprise Linux for ARM 64 - 4 years of updates 9.4 aarch64
• Red Hat Enterprise Linux for IBM z Systems - 4 years of updates 9.4 s390x
• Red Hat Enterprise Linux for x86_64 - Extended Life Cycle 9.4 x86_64
• Red Hat Enterprise Linux for ARM 64 - Extended Life Cycle 9.4 aarch64
• Red Hat Enterprise Linux for Power, little endian - Extended Life Cycle 9.4 ppc64le
• Red Hat Enterprise Linux for IBM z Systems - Extended Life Cycle 9.4 s390x

Fixes

• 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 - 2480757 - CVE-2026-27136 golang.org/x/net/html: golang: golang.org/x/net/html: Cross-Site Scripting via HTML parsing bypass
• BZ - 2480761 - CVE-2026-25681 golang.org/x/net/html: golang.org/x/net/html: Arbitrary code execution via Cross-Site Scripting
• BZ - 2480762 - CVE-2026-42502 golang.org/x/net/html: golang: golang.org/x/net/html: Cross-Site Scripting via unexpected HTML tree rendering

CVEs

• CVE-2026-25681
• CVE-2026-27136
• CVE-2026-39821
• CVE-2026-42502

References

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