RHSA-2026:26535 - Security Advisory

Topic

An update for kernel is now available for Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support and Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On.

Red Hat Product Security has rated this update as having a security impact of Critical. 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: geneve: Fix use-after-free in geneve_find_dev(). (CVE-2025-21858)
• kernel: sctp: fix a potential overflow in sctp_ifwdtsn_skip (CVE-2023-53372)
• kernel: net: use dst_dev_rcu() in sk_setup_caps() (CVE-2025-40170)
• kernel: ipv6: use RCU in ip6_xmit() (CVE-2025-40135)
• kernel: ipv6: use RCU in ip6_output() (CVE-2025-40158)
• kernel: nbd: defer config unlock in nbd_genl_connect (CVE-2025-68366)
• kernel: mlxsw: spectrum_mr: Fix use-after-free when updating multicast route stats (CVE-2025-68800)
• kernel: iommu: disable SVA when CONFIG_X86 is set (CVE-2025-71089)
• kernel: macvlan: fix possible UAF in macvlan_forward_source() (CVE-2026-23001)
• kernel: Linux kernel: Denial of Service due to a deadlock in hugetlb folio migration (CVE-2026-23097)
• kernel: ALSA: aloop: Fix racy access at PCM trigger (CVE-2026-23191)
• kernel: scsi: target: iscsi: Fix use-after-free in iscsit_dec_conn_usage_count() (CVE-2026-23216)
• kernel: Linux kernel: Denial of service and memory corruption in RDMA umad (CVE-2026-23243)
• kernel: netfilter: nf_tables: release flowtable after rcu grace period on error (CVE-2026-23392)
• kernel: netfilter: ip6t_eui64: reject invalid MAC header for all packets (CVE-2026-31685)
• kernel: ip6_tunnel: clear skb2->cb[] in ip4ip6_err() (CVE-2026-43037)
• kernel: ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach() (CVE-2026-43038)
• kernel: netfilter: ctnetlink: ensure safe access to master conntrack (CVE-2026-43116)
• kernel: wifi: brcmfmac: validate bsscfg indices in IF events (CVE-2026-43110)
• kernel: md/bitmap: fix GPF in write_page caused by resize race (CVE-2026-43163)
• kernel: netfilter: xt_tcpmss: check remaining length before reading optlen (CVE-2026-43190)
• kernel: xfs: fix freemap adjustments when adding xattrs to leaf blocks (CVE-2026-43158)
• kernel: Linux kernel: smb: client: reject userspace cifs.spnego descriptions (CVE-2026-46243)
• kernel: sctp: revalidate list cursor after sctp_sendmsg_to_asoc() in SCTP_SENDALL (CVE-2026-46227)

Bug Fix(es) and Enhancement(s):

• NFS client hangs while returning delegations (JIRA:RHEL-112276)
• Rhel backport of upstream commit "i40e: avoid redundant VF link state update" (JIRA:RHEL-141908)

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.

Affected Products

• Red Hat Enterprise Linux for x86_64 - Extended Life Cycle Long Life 8.4 x86_64
• Red Hat Enterprise Linux Server - AUS 8.4 x86_64

Fixes

• BZ - 2351619 - CVE-2025-21858 kernel: geneve: Fix use-after-free in geneve_find_dev().
• BZ - 2396405 - CVE-2023-53372 kernel: sctp: fix a potential overflow in sctp_ifwdtsn_skip
• BZ - 2414506 - CVE-2025-40170 kernel: net: use dst_dev_rcu() in sk_setup_caps()
• BZ - 2414521 - CVE-2025-40135 kernel: ipv6: use RCU in ip6_xmit()
• BZ - 2414523 - CVE-2025-40158 kernel: ipv6: use RCU in ip6_output()
• BZ - 2424881 - CVE-2025-68366 kernel: nbd: defer config unlock in nbd_genl_connect
• BZ - 2429065 - CVE-2025-68800 kernel: mlxsw: spectrum_mr: Fix use-after-free when updating multicast route stats
• BZ - 2429104 - CVE-2025-71089 kernel: iommu: disable SVA when CONFIG_X86 is set
• BZ - 2432664 - CVE-2026-23001 kernel: macvlan: fix possible UAF in macvlan_forward_source()
• BZ - 2436802 - CVE-2026-23097 kernel: Linux kernel: Denial of Service due to a deadlock in hugetlb folio migration
• BZ - 2439947 - CVE-2026-23191 kernel: ALSA: aloop: Fix racy access at PCM trigger
• BZ - 2440630 - CVE-2026-23216 kernel: scsi: target: iscsi: Fix use-after-free in iscsit_dec_conn_usage_count()
• BZ - 2448594 - CVE-2026-23243 kernel: Linux kernel: Denial of service and memory corruption in RDMA umad
• BZ - 2451218 - CVE-2026-23392 kernel: netfilter: nf_tables: release flowtable after rcu grace period on error
• BZ - 2461759 - CVE-2026-31685 kernel: netfilter: ip6t_eui64: reject invalid MAC header for all packets
• BZ - 2464351 - CVE-2026-43037 kernel: ip6_tunnel: clear skb2->cb[] in ip4ip6_err()
• BZ - 2464397 - CVE-2026-43038 kernel: ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()
• BZ - 2467005 - CVE-2026-43116 kernel: netfilter: ctnetlink: ensure safe access to master conntrack
• BZ - 2467014 - CVE-2026-43110 kernel: wifi: brcmfmac: validate bsscfg indices in IF events
• BZ - 2467059 - CVE-2026-43163 kernel: md/bitmap: fix GPF in write_page caused by resize race
• BZ - 2467064 - CVE-2026-43190 kernel: netfilter: xt_tcpmss: check remaining length before reading optlen
• BZ - 2467210 - CVE-2026-43158 kernel: xfs: fix freemap adjustments when adding xattrs to leaf blocks
• BZ - 2481486 - CVE-2026-46243 kernel: Linux kernel: smb: client: reject userspace cifs.spnego descriptions
• BZ - 2482564 - CVE-2026-46227 kernel: sctp: revalidate list cursor after sctp_sendmsg_to_asoc() in SCTP_SENDALL

CVEs

• CVE-2023-53372
• CVE-2025-21858
• CVE-2025-40135
• CVE-2025-40158
• CVE-2025-40170
• CVE-2025-68366
• CVE-2025-68800
• CVE-2025-71089
• CVE-2026-23001
• CVE-2026-23097
• CVE-2026-23191
• CVE-2026-23216
• CVE-2026-23243
• CVE-2026-23392
• CVE-2026-31685
• CVE-2026-43037
• CVE-2026-43038
• CVE-2026-43110
• CVE-2026-43116
• CVE-2026-43158
• CVE-2026-43163
• CVE-2026-43190
• CVE-2026-46227
• CVE-2026-46243

References

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