RHSA-2026:66016 — Security Advisory

An update for osbuild-composer is now available for Red Hat Enterprise Linux 8.

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.

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-fips: Golang FIPS zeroed buffer (CVE-2024-9355)

• golang: net/http: net/http: sensitive headers incorrectly sent after cross-domain redirect (CVE-2024-45336)

• net/mail: golang: Go net/mail: Denial of Service via crafted email inputs (CVE-2026-39820)

• golang.org/x/net/idna: golang: net/http: golang.org/x/net/idna: Privilege escalation via incorrect Punycode label processing (CVE-2026-39821)

• encoding/asn1: golang: Go encoding/asn1: Denial of Service via excessive recursion in Unmarshal (CVE-2026-33818)

• net/url: golang: golang net/url: Denial of Service from quadratic complexity in path resolution (CVE-2026-56860)

• net/http: golang: Go net/http: Unencrypted HTTP/2 connections vulnerable to Denial of Service (CVE-2026-56853)

• html/template: golang: Go html/template: Cross-Site Scripting via pathological input (CVE-2026-56858)

• crypto/tls: golang: Golang crypto/tls: Denial of Service via indefinite KeyUpdate messages (CVE-2026-56862)

• encoding/xml: golang: Go: Denial of Service via XML decoding recursion depth issue (CVE-2026-56859)

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.