RHSA-2026:90493HighCVSS 9.1

Red Hat Security Advisory: osbuild-composer security update

Published
October 26, 2026
Last Modified
November 2, 2026

🔗 CVE IDs covered (6)

CVE-2026-55677 →CVE-2026-111943 →CVE-2026-25681 →CVE-2026-27136 →CVE-2026-33186 →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-2026-33186 — google.golang.org/grpc/grpc-go: google.golang.org/grpc/authz: gRPC-Go: Authorization bypass due to improper HTTP/2 path validation CVE-2026-42502 — golang.org/x/net/html: golang: golang.org/x/net/html: Cross-Site Scripting via unexpected HTML tree rendering CVE-2026-55677 — github.com/labstack/echo: Echo: Unauthorized Information Disclosure via URL Path Decoding Discrepancy CVE-2026-111943 — crypto/x509: golang: crypto/x509: Man-in-the-middle attacks via untrusted intermediate certificates

🎯 Affected products22

  • Red Hat Enterprise Linux AppStream AUS (v.8.6)
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
  • osbuild-composer-0:46.3-11.el8_6.src as a component of Red Hat Enterprise Linux AppStream AUS (v.8.6)
  • osbuild-composer-0:46.3-11.el8_6.src as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
  • osbuild-composer-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.6)
  • osbuild-composer-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
  • osbuild-composer-core-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.6)
  • osbuild-composer-core-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
  • osbuild-composer-core-debuginfo-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.6)
  • osbuild-composer-core-debuginfo-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
  • osbuild-composer-debuginfo-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.6)
  • osbuild-composer-debuginfo-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
  • osbuild-composer-debugsource-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.6)
  • osbuild-composer-debugsource-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
  • osbuild-composer-dnf-json-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.6)
  • osbuild-composer-dnf-json-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
  • osbuild-composer-tests-debuginfo-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.6)
  • osbuild-composer-tests-debuginfo-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
  • osbuild-composer-worker-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.6)
  • osbuild-composer-worker-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
  • osbuild-composer-worker-debuginfo-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream AUS (v.8.6)
  • osbuild-composer-worker-debuginfo-0:46.3-11.el8_6.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)

✅ 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: To mitigate this issue, implement infrastructure-level normalization to ensure all incoming HTTP/2 `:path` headers are properly formatted with a leading slash before reaching the gRPC-Go server. This can be achieved by configuring a reverse proxy or API gateway to validate and normalize the `:path` header. Ensure that any such intermediary is properly configured and restarted to apply the changes, which may temporarily impact service availability. 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. Workaround: See the security bulletin for a detailed mitigation procedure.

🔗 References (9)