RHSA-2026:91587 - Security Advisory

Topic

An update for osbuild-composer is now available for Red Hat Enterprise Linux 9.6 Extended Update Support.

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):

• mime: golang: Golang MIME: Denial of Service via maliciously-crafted MIME header (CVE-2026-42504)
• google.golang.org/grpc: gRPC-Go: Denial of Service via malformed RPC requests (CVE-2026-84445)
• net/http: golang: golang: Denial of Service via crafted HTTP Range headers (CVE-2026-78667)
• crypto/tls: golang: crypto/tls: Denial of Service via multiple ECH outer extension references (CVE-2026-97031)
• net/textproto: mime/multipart: golang: golang: Denial of Service via memory limit bypass in multipart form parsing (CVE-2026-94440)
• net/http: net/http/internal/http2: golang.org/x/net/http2: net/http: Denial of Service via excessive HTTP/2 SETTINGS frames (CVE-2026-78669)
• 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 Update Support 9.6 x86_64
• Red Hat Enterprise Linux Server - AUS 9.6 x86_64
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 9.6 s390x
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 9.6 ppc64le
• Red Hat Enterprise Linux for ARM 64 - Extended Update Support 9.6 aarch64
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 9.6 ppc64le
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 9.6 x86_64
• Red Hat Enterprise Linux for ARM 64 - 4 years of updates 9.6 aarch64
• Red Hat Enterprise Linux for IBM z Systems - 4 years of updates 9.6 s390x
• Red Hat Enterprise Linux for x86_64 - Extended Life Cycle 9.6 x86_64
• Red Hat Enterprise Linux for ARM 64 - Extended Life Cycle 9.6 aarch64
• Red Hat Enterprise Linux for Power, little endian - Extended Life Cycle 9.6 ppc64le
• Red Hat Enterprise Linux for IBM z Systems - Extended Life Cycle 9.6 s390x

Fixes

• BZ - 2484204 - CVE-2026-42504 mime: golang: Golang MIME: Denial of Service via maliciously-crafted MIME header
• BZ - 2533175 - CVE-2026-84445 google.golang.org/grpc: gRPC-Go: Denial of Service via malformed RPC requests
• BZ - 2548334 - CVE-2026-78667 net/http: golang: golang: Denial of Service via crafted HTTP Range headers
• BZ - 2548336 - CVE-2026-97031 crypto/tls: golang: crypto/tls: Denial of Service via multiple ECH outer extension references
• BZ - 2548341 - CVE-2026-94440 net/textproto: mime/multipart: golang: golang: Denial of Service via memory limit bypass in multipart form parsing
• BZ - 2548344 - CVE-2026-78669 net/http: net/http/internal/http2: golang.org/x/net/http2: net/http: Denial of Service via excessive HTTP/2 SETTINGS frames
• BZ - 2556068 - CVE-2026-111943 crypto/x509: golang: crypto/x509: Man-in-the-middle attacks via untrusted intermediate certificates

CVEs

• CVE-2026-42504
• CVE-2026-78667
• CVE-2026-78669
• CVE-2026-84445
• CVE-2026-94440
• CVE-2026-97031
• CVE-2026-111943

References

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