RHSA-2026:89082 - Security Advisory

Topic

An update for kernel-rt 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.

Description

The kernel-rt packages provide the Real Time Linux Kernel, which enables fine-tuning for systems with extremely high determinism requirements.

Security Fix(es):

• kernel: tcp: restrict SO_ATTACH_FILTER to priv users (CVE-2026-53236)
• kernel: fuse: re-lock request before replacing page cache folio (CVE-2026-53388)
• kernel: writeback: fix race between cgroup_writeback_umount() and inode_switch_wbs() (CVE-2026-64378)
• kernel: net: gro: fix double aggregation of flush-marked skbs (CVE-2026-68136)
• kernel: net/packet: avoid fanout hook re-registration after unregister (CVE-2026-68338)
• kernel: net/iucv: fix use-after-free of a severed iucv_path (CVE-2026-68140)
• kernel: net/sched: serialize qdisc_rtab_list against concurrent get/put (CVE-2026-68138)
• kernel: ipvs: reload ip header after head reallocation (CVE-2026-68476)
• kernel: selinux: avoid sk_socket dereference in selinux_sctp_bind_connect() (CVE-2026-72242)
• kernel: mptcp: options: reset DSS fields in case of unexpected size (CVE-2026-80586)
• kernel: usb: usbfs: fix use-after-free of usb_device in usbdev_release() (CVE-2026-80824)
• kernel: smb: client: clear setuid/setgid bit on write with cifsacl/modefromsid/posix extensions (CVE-2026-89638)
• kernel: net/iucv: filter frames in afiucv_hs_rcv() by ingress device (CVE-2026-81003)
• kernel: ipv4: validate checksum_start before completing checksum (CVE-2026-99999)

Bug Fix(es) and Enhancement(s):

• Backport 6785011f8b16 ("ipv4: validate checksum_start before completing checksum") [rhel-8.10.z] (JIRA:RHEL-280584)

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 Real Time 8 x86_64
• Red Hat Enterprise Linux for Real Time for NFV 8 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Life Cycle 8.10 x86_64

Fixes

• BZ - 2492709 - CVE-2026-53236 kernel: tcp: restrict SO_ATTACH_FILTER to priv users
• BZ - 2502255 - CVE-2026-53388 kernel: fuse: re-lock request before replacing page cache folio
• BZ - 2507296 - CVE-2026-64378 kernel: writeback: fix race between cgroup_writeback_umount() and inode_switch_wbs()
• BZ - 2513163 - CVE-2026-68136 kernel: net: gro: fix double aggregation of flush-marked skbs
• BZ - 2513264 - CVE-2026-68338 kernel: net/packet: avoid fanout hook re-registration after unregister
• BZ - 2513293 - CVE-2026-68140 kernel: net/iucv: fix use-after-free of a severed iucv_path
• BZ - 2513343 - CVE-2026-68138 kernel: net/sched: serialize qdisc_rtab_list against concurrent get/put
• BZ - 2516417 - CVE-2026-72242 kernel: selinux: avoid sk_socket dereference in selinux_sctp_bind_connect()
• BZ - 2524438 - CVE-2026-80586 kernel: mptcp: options: reset DSS fields in case of unexpected size
• BZ - 2528642 - CVE-2026-80824 kernel: usb: usbfs: fix use-after-free of usb_device in usbdev_release()
• BZ - 2532122 - CVE-2026-89638 kernel: smb: client: clear setuid/setgid bit on write with cifsacl/modefromsid/posix extensions
• BZ - 2532515 - CVE-2026-81003 kernel: net/iucv: filter frames in afiucv_hs_rcv() by ingress device
• BZ - 2553429 - CVE-2026-99999 kernel: ipv4: validate checksum_start before completing checksum

CVEs

• CVE-2026-53236
• CVE-2026-53388
• CVE-2026-64378
• CVE-2026-68136
• CVE-2026-68138
• CVE-2026-68140
• CVE-2026-68338
• CVE-2026-68476
• CVE-2026-72242
• CVE-2026-80586
• CVE-2026-80824
• CVE-2026-81003
• CVE-2026-89638
• CVE-2026-99999

References

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