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High · 8.8 Public exploit CVE-2026-97555 EUVD-2026-86863GHSA-3qpp-vv65-cq9g

smb: client: fix heap overflow in DACL owner/group rewrite

Published Sep 25, 2026 · Updated Oct 30, 2026 · Assigned by Linux

Vendor: Linux Product: Linux Package: kernel Package: linux Package: linux Package: linux-6.12 Package: linux-allwinner-5.19 Package: linux-aws Package: linux-aws-5.0 Package: linux-aws-5.11 Package: linux-aws-5.13 Package: linux-aws-5.15 Package: linux-aws-5.19 Package: linux-aws-5.3 Package: linux-aws-5.8 Package: linux-aws-6.14 Package: linux-aws-6.17 Package: linux-aws-6.2 Package: linux-aws-6.5 Package: linux-aws-6.8 Package: linux-aws-7.0 Package: linux-aws-fips Package: linux-azure Package: linux-azure-5.11 Package: linux-azure-5.13 Package: linux-azure-5.15 Package: linux-azure-5.19 Package: linux-azure-5.3 Package: linux-azure-5.8 Package: linux-azure-6.11 Package: linux-azure-6.14 Package: linux-azure-6.17 Package: linux-azure-6.2 Package: linux-azure-6.5 Package: linux-azure-6.8 Package: linux-azure-7.0 Package: linux-azure-edge Package: linux-azure-fde Package: linux-azure-fde-5.15 Package: linux-azure-fde-5.19 Package: linux-azure-fde-6.14 Package: linux-azure-fde-6.17 Package: linux-azure-fde-6.2 Package: linux-azure-fde-6.8 Package: linux-azure-fde-7.0 Package: linux-azure-fips Package: linux-azure-nvidia Package: linux-azure-nvidia-6.14 Package: linux-bluefield Package: linux-fips Package: linux-gcp Package: linux-gcp-5.11 Package: linux-gcp-5.13 Package: linux-gcp-5.15 Package: linux-gcp-5.19 Package: linux-gcp-5.3 Package: linux-gcp-5.8 Package: linux-gcp-6.11 Package: linux-gcp-6.14 Package: linux-gcp-6.17 Package: linux-gcp-6.2 Package: linux-gcp-6.5 Package: linux-gcp-6.8 Package: linux-gcp-7.0 Package: linux-gcp-fips Package: linux-gke Package: linux-gke-4.15 Package: linux-gke-5.15 Package: linux-gke-5.4 Package: linux-gkeop Package: linux-gkeop-5.15 Package: linux-gkeop-5.4 Package: linux-hwe Package: linux-hwe-5.11 Package: linux-hwe-5.13 Package: linux-hwe-5.15 Package: linux-hwe-5.19 Package: linux-hwe-5.8 Package: linux-hwe-6.11 Package: linux-hwe-6.14 Package: linux-hwe-6.17 Package: linux-hwe-6.2 Package: linux-hwe-6.5 Package: linux-hwe-6.8 Package: linux-hwe-7.0 Package: linux-hwe-edge Package: linux-ibm Package: linux-ibm-5.15 Package: linux-ibm-6.8 Package: linux-intel-5.13 Package: linux-intel-iot-realtime Package: linux-intel-iotg Package: linux-intel-iotg-5.15 Package: linux-kvm Package: linux-lowlatency Package: linux-lowlatency-hwe-5.15 Package: linux-lowlatency-hwe-5.19 Package: linux-lowlatency-hwe-6.11 Package: linux-lowlatency-hwe-6.2 Package: linux-lowlatency-hwe-6.5 Package: linux-lowlatency-hwe-6.8 Package: linux-nvidia Package: linux-nvidia-6.11 Package: linux-nvidia-6.17 Package: linux-nvidia-6.2 Package: linux-nvidia-6.5 Package: linux-nvidia-6.8 Package: linux-nvidia-7.0 Package: linux-nvidia-bos Package: linux-nvidia-lowlatency Package: linux-nvidia-tegra Package: linux-nvidia-tegra-5.15 Package: linux-nvidia-tegra-igx Package: linux-oem Package: linux-oem-5.10 Package: linux-oem-5.13 Package: linux-oem-5.14 Package: linux-oem-5.17 Package: linux-oem-5.6 Package: linux-oem-6.0 Package: linux-oem-6.1 Package: linux-oem-6.11 Package: linux-oem-6.14 Package: linux-oem-6.17 Package: linux-oem-6.5 Package: linux-oem-6.8 Package: linux-oem-7.0 Package: linux-oracle Package: linux-oracle-5.0 Package: linux-oracle-5.11 Package: linux-oracle-5.13 Package: linux-oracle-5.15 Package: linux-oracle-5.3 Package: linux-oracle-5.8 Package: linux-oracle-6.14 Package: linux-oracle-6.17 Package: linux-oracle-6.5 Package: linux-oracle-6.8 Package: linux-oracle-7.0 Package: linux-raspi Package: linux-raspi-realtime Package: linux-raspi2 Package: linux-realtime Package: linux-realtime-6.14 Package: linux-realtime-6.17 Package: linux-realtime-6.8 Package: linux-riscv Package: linux-riscv-5.11 Package: linux-riscv-5.15 Package: linux-riscv-5.19 Package: linux-riscv-5.8 Package: linux-riscv-6.14 Package: linux-riscv-6.17 Package: linux-riscv-6.5 Package: linux-riscv-6.8 Package: linux-riscv-7.0 Package: linux-starfive-5.19 Package: linux-starfive-6.2 Package: linux-starfive-6.5 Package: linux-vmware Package: linux-xilinx Package: linux-xilinx-zynqmp Platform: Linux Ecosystem: Azure Linux Ecosystem: Debian Ecosystem: Ubuntu

Description

In the Linux kernel, the following vulnerability has been resolved:

smb: client: fix heap overflow in DACL owner/group rewrite

When id_mode_to_cifs_acl rewrites an existing DACL, it allocates a
buffer sized according to the on-disk DACL length reported by
dacl_ptr->size. However, replace_sids_and_copy_aces may rewrite each
ACE with a new owner/group SID obtained from the cifs.idmap upcall.
Those SIDs can have up to SID_MAX_SUB_AUTHORITIES (15) sub-authorities,
making each ACE up to 76 bytes (sizeof(struct smb_ace)).

If the original DACL contains short SIDs (e.g., 1 sub-authority) while
the replacement SIDs are long, the rewritten ACEs overflow the
allocation.

Fix this by always budgeting for worst-case SID expansion: allocate
sizeof(struct smb_acl) plus num_aces * sizeof(struct smb_ace), which
covers the smb_acl header and room for every ACE at maximum SID size.
This replaces the previous split logic that used dacl_ptr->size for
cifsacl mounts but num_aces * sizeof(struct smb_ace) for mode_from_sid
mounts: both paths can trigger the same rewrite and need the same
headroom.

KASAN reports this as:
BUG: KASAN: slab-out-of-bounds in build_sec_desc+0x1e8a/0x2680 [cifs]
Write of size 4 at addr ffff8881a5e25374 by task chown/5298
...
The buggy address is located 0 bytes to the right of
allocated 884-byte region [ffff8881a5e25000, ffff8881a5e25374)

Affected products

VendorProductAffectedFixed
Linux Linux 5.12 5.15.224

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
Debian 14 linux 7.2.7-1 —
Debian 13 linux 6.12.111-1 —
Debian 12 linux No fix yet —
Debian 12 linux-6.12 6.12.111-1~deb12u1 —
ReleasePackageFixed inAdvisory
Ubuntu Nvidia-BlueField 24.04 LTS linux-bluefield 6.8.0-1036.41 —
Ubuntu Nvidia-BlueField 22.04 LTS linux-bluefield No fix yet —
Ubuntu 26.04 LTS linux 7.0.0-42.42 USN-8959-1
Ubuntu 26.04 LTS linux-aws 7.0.0-1016.17 USN-8959-1
Ubuntu 26.04 LTS linux-azure 7.0.0-1020.21 USN-9019-1
Ubuntu 26.04 LTS linux-azure-fde 7.0.0-1019.19 USN-9020-1
Ubuntu 26.04 LTS linux-gcp 7.0.0-1016.18 USN-8959-1
Ubuntu 26.04 LTS linux-gke 7.0.0-1010.11 USN-9020-1
Ubuntu 26.04 LTS linux-ibm +1 7.0.0-1017.17 USN-8960-1, USN-8959-1
Ubuntu 26.04 LTS linux-nvidia +1 No fix yet —
Ubuntu 26.04 LTS linux-oracle 7.0.0-1015.16 USN-8959-1
Ubuntu 26.04 LTS linux-raspi 7.0.0-1023.23 USN-9021-1
Ubuntu 26.04 LTS linux-realtime 7.0.0-43.43.1 USN-9020-1
Ubuntu 26.04 LTS linux-riscv 7.0.0-42.42.1 —
Ubuntu 24.04 LTS linux 6.8.0-149.149 USN-9022-1
Ubuntu 24.04 LTS linux-aws 6.8.0-1069.74 USN-9022-1
Ubuntu 24.04 LTS linux-aws-7.0 7.0.0-1017.18~24.04.1 USN-9020-1
Ubuntu 24.04 LTS linux-azure 6.8.0-1073.82 USN-9022-1
Ubuntu 24.04 LTS linux-azure-fde 6.8.0-1071.78 USN-9039-1
Ubuntu 24.04 LTS linux-azure-fde-7.0 7.0.0-1019.19~24.04.1 USN-9020-1
Ubuntu 24.04 LTS linux-gcp 6.8.0-1073.81 USN-9022-1
Ubuntu 24.04 LTS linux-gcp-7.0 7.0.0-1017.19~24.04.1 USN-9020-1
Ubuntu 24.04 LTS linux-gke 6.8.0-1068.77 USN-9022-1
Ubuntu 24.04 LTS linux-gkeop 6.8.0-1053.57 USN-9023-1
Ubuntu 24.04 LTS linux-hwe-7.0 7.0.0-42.42~24.04.1 USN-8959-1
Ubuntu 24.04 LTS linux-ibm 6.8.0-1069.70 USN-9022-1
Ubuntu 24.04 LTS linux-lowlatency 6.8.0-149.149.1 USN-9022-1
Ubuntu 24.04 LTS linux-nvidia 6.8.0-1067.70 USN-9024-1
Ubuntu 24.04 LTS linux-nvidia-lowlatency 6.8.0-1067.70.1 USN-9040-1
Ubuntu 24.04 LTS linux-oracle 6.8.0-1067.71 USN-9022-1
Ubuntu 24.04 LTS linux-oracle-7.0 7.0.0-1016.18~24.04.1 USN-9020-1
Ubuntu 24.04 LTS linux-raspi 6.8.0-1068.72 USN-9025-1
Ubuntu 24.04 LTS linux-riscv +32 No fix yet —
Ubuntu 24.04 LTS linux-riscv-7.0 7.0.0-42.42.1~24.04.1 —
Ubuntu 24.04 LTS linux-vmware 6.8.0-1010.10 USN-9022-1
Ubuntu 22.04 LTS linux +50 No fix yet —
Ubuntu 22.04 LTS linux-aws-6.8 6.8.0-1069.74~22.04.1 USN-9024-1
Ubuntu 22.04 LTS linux-azure-6.8 6.8.0-1073.82~22.04.1 USN-9026-1
Ubuntu 22.04 LTS linux-azure-fde-6.8 6.8.0-1071.78~22.04.1 USN-9026-1
Ubuntu 22.04 LTS linux-gcp-6.8 6.8.0-1073.81~22.04.1 USN-9024-1
Ubuntu 22.04 LTS linux-hwe-6.8 6.8.0-149.149~22.04.1 USN-9066-1
Ubuntu 22.04 LTS linux-ibm-6.8 6.8.0-1069.70~22.04.1 USN-9024-1
Ubuntu 22.04 LTS linux-lowlatency-hwe-6.8 6.8.0-149.149.1~22.04.1 USN-9024-1
Ubuntu 22.04 LTS linux-oracle-6.8 6.8.0-1067.71~22.04.1 USN-9025-1
Show 9 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Ubuntu 20.04 LTS linux-gke +28 No fix yet —
Ubuntu 18.04 LTS linux-gcp +14 No fix yet —
Ubuntu 16.04 LTS linux-hwe-edge No fix yet —
Ubuntu Pro Realtime 24.04 LTS linux-raspi-realtime 6.8.0-2056.58 USN-9025-1
Ubuntu Pro Realtime 24.04 LTS linux-realtime 6.8.1-1064.65 USN-9023-1
Ubuntu Pro Realtime 24.04 LTS linux-realtime-6.14 +1 No fix yet —
Ubuntu Pro Realtime 22.04 LTS linux-realtime +1 No fix yet —
Ubuntu Pro Realtime 22.04 LTS linux-realtime-6.8 6.8.1-1064.65~22.04.1 USN-9024-1
Ubuntu Pro FIPS-updates 24.04 LTS linux-aws-fips 6.8.0-1069.74+fips1 USN-9023-1
Ubuntu Pro FIPS-updates 24.04 LTS linux-azure-fips 6.8.0-1073.82+fips1 USN-9022-1
Ubuntu Pro FIPS-updates 24.04 LTS linux-fips No fix yet —
Ubuntu Pro FIPS-updates 24.04 LTS linux-gcp-fips 6.8.0-1073.81+fips1 USN-9023-1
Ubuntu Pro FIPS-updates 22.04 LTS linux-fips +3 No fix yet —
Ubuntu Pro FIPS-preview 22.04 LTS linux-fips +3 No fix yet —
Ubuntu Pro 20.04 LTS linux-aws-5.15 +10 No fix yet —
ReleasePackageFixed inAdvisory
SLES 15 SP7 kernel-64kb +5 6.4.0-150700.53.87.3 SUSE-SU-2026:4935-1
SLES 15 SP7 kernel-default-base 6.4.0-150700.53.87.3.150700.17.49.2 SUSE-SU-2026:4935-1
SLES 15 SP7 kernel-obs-build 6.4.0-150700.53.87.2 SUSE-SU-2026:4935-1
SLES 15 SP7 kernel-syms 6.4.0-150700.53.87.1 SUSE-SU-2026:4935-1
SLES 15 SP6 kernel-64kb +6 6.4.0-150600.23.143.1 SUSE-SU-2026:4934-1
SLES 15 SP6 kernel-default-base 6.4.0-150600.23.143.1.150600.12.66.3 SUSE-SU-2026:4934-1
SLES 15 SP5 kernel-64kb +6 5.14.21-150500.55.195.1 SUSE-SU-2026:4936-1
SLES 15 SP5 kernel-default-base 5.14.21-150500.55.195.1.150500.6.91.1 SUSE-SU-2026:4936-1
SLES 15 SP4 kernel-64kb +6 5.14.21-150400.24.246.1 SUSE-SU-2026:4937-1
SLES 15 SP4 kernel-default-base 5.14.21-150400.24.246.1.150400.24.124.1 SUSE-SU-2026:4937-1
Show 18 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
SLES for SAP 16.0 kernel-64kb +8 6.12.0-160000.40.1 SUSE-SU-2026:24446-1
SLES for SAP 16.0 kernel-default-base 6.12.0-160000.40.1.160000.2.29 SUSE-SU-2026:24446-1
SLES for SAP 15 SP6 kernel-default-base 6.4.0-150600.23.143.1.150600.12.66.3 SUSE-SU-2026:4934-1
SLES for SAP 15 SP6 kernel-docs +4 6.4.0-150600.23.143.1 SUSE-SU-2026:4934-1
SLES for SAP 15 SP5 kernel-default-base 5.14.21-150500.55.195.1.150500.6.91.1 SUSE-SU-2026:4936-1
SLES for SAP 15 SP5 kernel-docs +4 5.14.21-150500.55.195.1 SUSE-SU-2026:4936-1
SLES for SAP 15 SP4 kernel-default-base 5.14.21-150400.24.246.1.150400.24.124.1 SUSE-SU-2026:4937-1
SLES for SAP 15 SP4 kernel-docs +4 5.14.21-150400.24.246.1 SUSE-SU-2026:4937-1
SLES 16.0 kernel-64kb +8 6.12.0-160000.40.1 SUSE-SU-2026:24446-1, SUSE-SU-2026:24437-1
SLES 16.0 kernel-default-base 6.12.0-160000.40.1.160000.2.29 SUSE-SU-2026:24446-1
SLE Micro 6.2 kernel-default-base 6.12.0-160000.40.1.160000.2.29 SUSE-SU-2026:24422-1
SLE Micro 6.2 kernel-rt +5 6.12.0-160000.40.1 SUSE-SU-2026:24422-1, SUSE-SU-2026:24386-1
SLE Micro 6.1 kernel-default-base 6.4.0-159998.54.1.159998.21.39 SUSE-SU-2026:24379-1
SLE Micro 6.1 kernel-rt +4 6.4.0-159998.54.1 SUSE-SU-2026:24553-1, SUSE-SU-2026:24379-1
SLE Micro 6.0 kernel-default-base 6.4.0-159998.54.1.159998.21.40 SUSE-SU-2026:24371-1
SLE Micro 6.0 kernel-rt +4 6.4.0-159998.54.1 SUSE-SU-2026:24473-1, SUSE-SU-2026:24371-1
SLE Micro 5.5 kernel-default-base 5.14.21-150500.55.195.1.150500.6.91.1 SUSE-SU-2026:4936-1
SLE Micro 5.5 kernel-rt +1 5.14.21-150500.13.167.2 SUSE-SU-2026:4938-1
SLE Micro 5.5 kernel-source +1 5.14.21-150500.55.195.1 SUSE-SU-2026:4936-1
SLE Micro 5.4 kernel-default-base 5.14.21-150400.24.246.1.150400.24.124.1 SUSE-SU-2026:4937-1
SLE Micro 5.4 kernel-rt +1 5.14.21-150400.15.192.2 SUSE-SU-2026:4939-1
SLE Micro 5.4 kernel-source +1 5.14.21-150400.24.246.1 SUSE-SU-2026:4937-1
SLE Micro 5.3 kernel-default-base 5.14.21-150400.24.246.1.150400.24.124.1 SUSE-SU-2026:4937-1
SLE Micro 5.3 kernel-source +1 5.14.21-150400.24.246.1 SUSE-SU-2026:4937-1
SLE Live Patching 15 SP7 kernel-default 6.4.0-150700.53.87.3 SUSE-SU-2026:4935-1
SLE Live Patching 15 SP7 kernel-livepatch-SLE15-SP7-RT_Update_22 1-150700.1.3.1 SUSE-SU-2026:4940-1
SLE Live Patching 15 SP7 kernel-livepatch-SLE15-SP7_Update_23 1-150700.15.3.2 SUSE-SU-2026:4935-1
SLE Live Patching 15 SP6 kernel-default 6.4.0-150600.23.143.1 SUSE-SU-2026:4934-1
SLE Live Patching 15 SP6 kernel-livepatch-SLE15-SP6_Update_33 1-150600.13.5.1 SUSE-SU-2026:4934-1
SLE Live Patching 15 SP5 kernel-default 5.14.21-150500.55.195.1 SUSE-SU-2026:4936-1
SLE Live Patching 15 SP5 kernel-livepatch-SLE15-SP5_Update_47 1-150500.11.3.1 SUSE-SU-2026:4936-1
SLE Live Patching 15 SP4 kernel-default 5.14.21-150400.24.246.1 SUSE-SU-2026:4937-1
SLE Live Patching 15 SP4 kernel-livepatch-SLE15-SP4_Update_61 1-150400.9.3.1 SUSE-SU-2026:4937-1
SLE HPC 15 SP5 kernel-64kb +5 5.14.21-150500.55.195.1 SUSE-SU-2026:4936-1
SLE HPC 15 SP5 kernel-default-base 5.14.21-150500.55.195.1.150500.6.91.1 SUSE-SU-2026:4936-1
SLE HPC 15 SP4 kernel-64kb +5 5.14.21-150400.24.246.1 SUSE-SU-2026:4937-1
SLE HPC 15 SP4 kernel-default-base 5.14.21-150400.24.246.1.150400.24.124.1 SUSE-SU-2026:4937-1
SUSE Real Time Module 15 SP7 kernel-rt +2 6.4.0-150700.7.81.1 SUSE-SU-2026:4940-1
ReleasePackageFixed inAdvisory
openSUSE Tumbleweed kernel-source 7.2.9-1.1 openSUSE-SU-2026:12074-1
openSUSE Leap 16.0 kernel-default-base 6.12.0-160000.40.1.160000.2.29 openSUSE-SU-2026:22167-1
openSUSE Leap 16.0 kernel-rt +11 6.12.0-160000.40.1 openSUSE-SU-2026:22167-1

Amazon Linux

ReleasePackageFixed inAdvisory
Amazon Linux 2023 kernel-livepatch-6.1.174-217.345 +2 1:1.0-0.amzn2023 ALAS2023-2026-3193, ALAS2023-2026-3192, ALAS2023-2026-1817
Amazon Linux 2023 perf +11 1:6.1.174-217.345.amzn2023 ALAS2023-2026-1817
Amazon Linux 2023 perf6.12 +11 1:6.12.111-136.204.amzn2023 ALAS2023-2026-3193
Amazon Linux 2023 perf6.18 +12 1:6.18.54-121.166.amzn2023 ALAS2023-2026-3192

Azure Linux

ReleasePackageFixed inAdvisory
Azure Linux 3 kernel 6.6.158.1-1 —

Oracle Linux

ReleasePackageFixed inAdvisory
Oracle Linux 9 kernel-uek +34 6.12.0-207.111.5.1.el10uek ELSA-2026-500374

Public exploits

Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.

Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.

GitHub 1 repository

  • woshigenm/CVE-2026-97555 ★ 4 · Oct 29, 2026

    CVE-2026-97555: heap overflow in the Linux SMB client DACL rewrite (cifs.ko) — analysis, POC, and an arm64 exploit chain ending in a uid-0 credential overwrite on the reference build

Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.

Advisories 35

References