RHSA-2026:59562HighCVSS 8.2

Red Hat Security Advisory: osbuild-composer security update

Published
August 25, 2026
Last Modified
August 30, 2026

🔗 CVE IDs covered (4)

CVE-2026-25681 →CVE-2026-27136 →CVE-2026-39821 →CVE-2026-42502 →

📋 Description

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

🎯 Affected products34

  • Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-0:101.3-4.el9_4.5.aarch64 as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-0:101.3-4.el9_4.5.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-0:101.3-4.el9_4.5.s390x as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-0:101.3-4.el9_4.5.src as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-0:101.3-4.el9_4.5.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-core-0:101.3-4.el9_4.5.aarch64 as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-core-0:101.3-4.el9_4.5.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-core-0:101.3-4.el9_4.5.s390x as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-core-0:101.3-4.el9_4.5.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-core-debuginfo-0:101.3-4.el9_4.5.aarch64 as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-core-debuginfo-0:101.3-4.el9_4.5.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-core-debuginfo-0:101.3-4.el9_4.5.s390x as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-core-debuginfo-0:101.3-4.el9_4.5.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-debuginfo-0:101.3-4.el9_4.5.aarch64 as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-debuginfo-0:101.3-4.el9_4.5.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-debuginfo-0:101.3-4.el9_4.5.s390x as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-debuginfo-0:101.3-4.el9_4.5.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-debugsource-0:101.3-4.el9_4.5.aarch64 as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-debugsource-0:101.3-4.el9_4.5.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-debugsource-0:101.3-4.el9_4.5.s390x as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-debugsource-0:101.3-4.el9_4.5.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-tests-debuginfo-0:101.3-4.el9_4.5.aarch64 as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-tests-debuginfo-0:101.3-4.el9_4.5.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-tests-debuginfo-0:101.3-4.el9_4.5.s390x as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-tests-debuginfo-0:101.3-4.el9_4.5.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-worker-0:101.3-4.el9_4.5.aarch64 as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-worker-0:101.3-4.el9_4.5.ppc64le as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-worker-0:101.3-4.el9_4.5.s390x as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • osbuild-composer-worker-0:101.3-4.el9_4.5.x86_64 as a component of Red Hat Enterprise Linux AppStream E4S (v.9.4)
  • +4 more not shown

✅ Remediation

For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 Workaround: To mitigate this flaw, applications processing untrusted HTML input must implement strict input sanitization and ensure all output is properly encoded before rendering. Deploying a comprehensive Content Security Policy (CSP) can restrict script execution, further reducing the attack surface. Administrators should review application configurations to ensure adequate protection against XSS. Workaround: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. Workaround: Upgrade to a fixed golang.org/x/net release that includes the idna correction, via updated golang or dependent package rebuilds. Workaround: Applications utilizing `golang.org/x/net/html` should implement robust sanitization of all untrusted HTML input before rendering to prevent the creation of unexpected HTML structures that could facilitate XSS attacks. If an application does not require rendering arbitrary HTML, it should avoid processing such input.

🔗 References (7)