RHSA-2026:90493 - Security Advisory

Topic

An update for osbuild-composer is now available for Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support and Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On.

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):

• google.golang.org/grpc/grpc-go: google.golang.org/grpc/authz: gRPC-Go: Authorization bypass due to improper HTTP/2 path validation (CVE-2026-33186)
• 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)
• github.com/labstack/echo: Echo: Unauthorized Information Disclosure via URL Path Decoding Discrepancy (CVE-2026-55677)
• crypto/x509: golang: crypto/x509: Man-in-the-middle attacks via untrusted intermediate certificates (CVE-2026-111943)

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 for x86_64 - Extended Life Cycle Long Life 8.6 x86_64
• Red Hat Enterprise Linux Server - AUS 8.6 x86_64

Fixes

• BZ - 2449833 - 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
• 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
• BZ - 2493622 - CVE-2026-55677 github.com/labstack/echo: Echo: Unauthorized Information Disclosure via URL Path Decoding Discrepancy
• BZ - 2556068 - CVE-2026-111943 crypto/x509: golang: crypto/x509: Man-in-the-middle attacks via untrusted intermediate certificates

CVEs

• CVE-2026-25681
• CVE-2026-27136
• CVE-2026-33186
• CVE-2026-42502
• CVE-2026-55677
• CVE-2026-111943

References

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