This Red Hat kernel security update addresses three high-severity vulnerabilities: an out-of-bounds read in the CIFS client (CVE-2026-43112, CVSS 8.8), a privilege escalation via improper CPU cache isolation on AMD Zen 2 processors (CVE-2025-54518, CVSS 7.0), and a use-after-free issue in the network traffic control action API (CVE-2026-53264, CVSS 7.8). The specific affected Linux kernel version ranges are extensive and vary per CVE; for example, CVE-2026-43112 affects versions from 5.16.1 up to but excluding 6.6.136, from 6.7 up to 6.12.83, from 6.13 up to 6.18.24, and from 6.19 up to 6.19.14. The fixed versions are also CVE-specific, such as upgrading to at least kernel 6.6.136, 6.12.83, 6.18.24, or 6.19.14 to resolve CVE-2026-43112.
Red Hat Product Errata RHSA-2026:53990 - Security Advisory Issued: 2026-08-12 Updated: 2026-08-12 RHSA-2026:53990 - Security Advisory Overview Updated Packages Synopsis Important: kernel security, bug fix, and enhancement update Type/Severity Security Advisory: Important Red Hat Lightspeed patch analysis Identify and remediate systems affected by this advisory. View affected systems Topic An update for kernel 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 The kernel packages contain the Linux kernel, the core of any Linux operating system. Security Fix(es): kernel: fs/smb/client: fix out-of-bounds read in cifs_sanitize_prepath (CVE-2026-43112) kernel: xen: AMD Zen 2 Processors: Privilege escalation via improper CPU cache isolation (CVE-2025-54518) kernel: net/sched: act_api: use RCU with deferred freeing for action lifecycle (CVE-2026-53264) Bug Fix(es) and Enhancement(s): [HPE-PL 9.9 Bug] Kernel call trace observed when access Intel Granite Rapids-D UART [rhel-9.6.z] (JIRA:RHEL-185342) [RHEL 9.4] Kernel memory reclaim bug [rhel-9.6.z] (JIRA:RHEL-211056) general protection fault during exportfs / nfsd4_revoke_states [rhel-9.6.z] (JIRA:RHEL-188255) 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 The system must be rebooted for this update to take effect. Red Hat recommends treating all kernel errata as security-relevant. Given the kernel's fundamental role, any bug has a higher chance of impacting system security, even if that impact only becomes clear after a fix is published. Therefore, Red Hat prioritizes delivering fixes that improve our customers' overall security posture. Because of this proactive approach, a patch may be associated with a CVE assignment at a future date. Retroactive CVE assignments are always documented in the corresponding errata and on Red Hat's CVE pages. We strongly advise against delaying updates, as doing so may leave your system exposed when protections are already available. 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 CodeReady Linux Builder for x86_64 - Extended Update Support 9.6 x86_64 Red Hat CodeReady Linux Builder for Power, little endian - Extended Update Support 9.6 ppc64le Red Hat CodeReady Linux Builder for IBM z Systems - Extended Update Support 9.6 s390x Red Hat CodeReady Linux Builder for ARM 64 - Extended Update Support 9.6 aarch64 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 - 2467015 - CVE-2026-43112 kernel: fs/smb/client: fix out-of-bounds read in cifs_sanitize_prepath BZ - 2477784 - CVE-2025-54518 kernel: xen: AMD Zen 2 Processors: Privilege escalation via improper CPU cache isolation BZ - 2492851 - CVE-2026-53264 kernel: net/sched: act_api: use RCU with deferred freeing for action lifecycle CVEs CVE-2025-54518 CVE-2026-43112 CVE-2026-53264 References https://access.redhat.com/security/updates/classification/#important Note: More recent versions of these packages may be available. Click a package name for more details. 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