Skip to content
OpenAdvisories
High · 8.8 CVE-2026-31709 EUVD-2026-26518GHSA-8hp2-qmc6-f97h

smb: client: validate the whole DACL before rewriting it in cifsacl

Published May 1, 2026 · Updated Oct 19, 2026 · Assigned by Linux

Vendor: Linux Product: Linux Package: kernel Package: linux Package: linux 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-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-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-6.2 Package: linux-azure-fde-6.8 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-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-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-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-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-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: validate the whole DACL before rewriting it in cifsacl

build_sec_desc() and id_mode_to_cifs_acl() derive a DACL pointer from a
server-supplied dacloffset and then use the incoming ACL to rebuild the
chmod/chown security descriptor.

The original fix only checked that the struct smb_acl header fits before
reading dacl_ptr->size or dacl_ptr->num_aces. That avoids the immediate
header-field OOB read, but the rewrite helpers still walk ACEs based on
pdacl->num_aces with no structural validation of the incoming DACL body.

A malicious server can return a truncated DACL that still contains a
header, claims one or more ACEs, and then drive
replace_sids_and_copy_aces() or set_chmod_dacl() past the validated
extent while they compare or copy attacker-controlled ACEs.

Factor the DACL structural checks into validate_dacl(), extend them to
validate each ACE against the DACL bounds, and use the shared validator
before the chmod/chown rebuild paths. parse_dacl() reuses the same
validator so the read-side parser and write-side rewrite paths agree on
what constitutes a well-formed incoming DACL.

Affected products

VendorProductAffectedFixed
Linux Linux 5.12 5.15.210

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 7.0.3-1 —
Debian 13 linux 6.12.86-1 —
Debian 12 linux 6.1.176-1 —
ReleasePackageFixed inAdvisory
Ubuntu Nvidia-BlueField 24.04 LTS linux-bluefield 6.8.0-1028.33 —
Ubuntu Nvidia-BlueField 22.04 LTS linux-bluefield 5.15.0-1101.103 —
Ubuntu 26.04 LTS linux 7.0.0-27.27 USN-8488-1
Ubuntu 26.04 LTS linux-aws 7.0.0-1008.8 USN-8488-1
Ubuntu 26.04 LTS linux-azure 7.0.0-1010.10 USN-8603-1
Ubuntu 26.04 LTS linux-gcp +1 7.0.0-1007.7 USN-8488-1
Ubuntu 26.04 LTS linux-ibm +1 7.0.0-1009.9 USN-8603-1, USN-8488-1
Ubuntu 26.04 LTS linux-nvidia 7.0.0-1013.13 USN-8507-1
Ubuntu 26.04 LTS linux-raspi 7.0.0-1014.14 USN-8488-2
Ubuntu 26.04 LTS linux-riscv +1 7.0.0-27.27.1 USN-8488-1
Ubuntu 25.10 linux +8 No fix yet —
Ubuntu 24.04 LTS linux 6.8.0-136.136 USN-8567-1
Ubuntu 24.04 LTS linux-aws 6.8.0-1061.64 USN-8595-2
Ubuntu 24.04 LTS linux-azure 6.8.0-1063.71 USN-8606-1
Ubuntu 24.04 LTS linux-azure-fde 6.8.0-1062.69 USN-8607-1
Ubuntu 24.04 LTS linux-gcp 6.8.0-1064.72 USN-8567-1
Ubuntu 24.04 LTS linux-gke 6.8.0-1059.67 USN-8567-1
Ubuntu 24.04 LTS linux-gkeop 6.8.0-1046.50 USN-8567-1
Ubuntu 24.04 LTS linux-hwe-7.0 7.0.0-28.28~24.04.1 USN-8569-1
Ubuntu 24.04 LTS linux-ibm 6.8.0-1061.62 USN-8574-3
Ubuntu 24.04 LTS linux-lowlatency 6.8.0-136.136.2 USN-8574-2
Ubuntu 24.04 LTS linux-nvidia 6.8.0-1059.62 USN-8596-1
Ubuntu 24.04 LTS linux-nvidia-lowlatency 6.8.0-1059.62.1 USN-8596-1
Ubuntu 24.04 LTS linux-nvidia-tegra 6.8.0-1030.31 USN-8574-3
Ubuntu 24.04 LTS linux-oracle 6.8.0-1058.61 USN-8574-2
Ubuntu 24.04 LTS linux-raspi 6.8.0-1061.65 USN-8665-1
Ubuntu 24.04 LTS linux-riscv +27 No fix yet —
Ubuntu 24.04 LTS linux-vmware 6.8.0-1008.8 —
Ubuntu 24.04 LTS linux-xilinx 6.8.0-1033.34 USN-8574-3
Show 10 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Ubuntu 22.04 LTS linux 5.15.0-198.208 USN-8875-1
Ubuntu 22.04 LTS linux-aws 5.15.0-1117.124 USN-8875-1
Ubuntu 22.04 LTS linux-aws-6.8 6.8.0-1061.64~22.04.1 USN-8595-3
Ubuntu 22.04 LTS linux-azure 5.15.0-1123.132 USN-8875-1
Ubuntu 22.04 LTS linux-azure-6.8 6.8.0-1063.71~22.04.1 USN-8606-1
Ubuntu 22.04 LTS linux-azure-fde 5.15.0-1122.131 USN-8876-1
Ubuntu 22.04 LTS linux-azure-fde-6.8 6.8.0-1062.69~22.04.1 USN-8609-1
Ubuntu 22.04 LTS linux-gcp 5.15.0-1118.128 USN-8877-1
Ubuntu 22.04 LTS linux-gcp-6.8 6.8.0-1064.72~22.04.1 USN-8567-1
Ubuntu 22.04 LTS linux-gke 5.15.0-1113.119 USN-8875-1
Ubuntu 22.04 LTS linux-gkeop 5.15.0-1100.108 USN-8875-1
Ubuntu 22.04 LTS linux-hwe-6.8 6.8.0-136.136~22.04.1 USN-8619-1
Ubuntu 22.04 LTS linux-ibm 5.15.0-1111.115 USN-8875-1
Ubuntu 22.04 LTS linux-ibm-6.8 6.8.0-1061.62~22.04.1 USN-8574-3
Ubuntu 22.04 LTS linux-intel-iotg 5.15.0-1112.118 USN-8875-1
Ubuntu 22.04 LTS linux-kvm 5.15.0-1109.114 USN-8875-1
Ubuntu 22.04 LTS linux-lowlatency 5.15.0-195.205 USN-8875-1
Ubuntu 22.04 LTS linux-lowlatency-hwe-6.8 6.8.0-136.136.2~22.04.1 USN-8574-2
Ubuntu 22.04 LTS linux-nvidia 5.15.0-1112.113 USN-8875-2
Ubuntu 22.04 LTS linux-nvidia-6.8 6.8.0-1059.62~22.04.1 USN-8596-1
Ubuntu 22.04 LTS linux-nvidia-tegra 5.15.0-1070.72 USN-8963-1
Ubuntu 22.04 LTS linux-nvidia-tegra-igx 5.15.0-1059.59 USN-8963-1
Ubuntu 22.04 LTS linux-oracle 5.15.0-1114.120 USN-8875-1
Ubuntu 22.04 LTS linux-oracle-6.8 6.8.0-1058.61~22.04.1 USN-8595-1
Ubuntu 22.04 LTS linux-raspi 5.15.0-1113.116 USN-9029-1
Ubuntu 22.04 LTS linux-riscv +32 No fix yet —
Ubuntu 22.04 LTS linux-riscv-6.8 6.8.0-136.136~22.04.3 —
Ubuntu 22.04 LTS linux-xilinx-zynqmp 5.15.0-1080.84 USN-8875-1
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 6.8.0-2050.52 USN-8665-1
Ubuntu Pro Realtime 24.04 LTS linux-realtime 6.8.1-1056.57 USN-8567-1
Ubuntu Pro Realtime 24.04 LTS linux-realtime-6.14 +1 No fix yet —
Ubuntu Pro Realtime 22.04 LTS linux-intel-iot-realtime 5.15.0-1109.111 USN-8875-1
Ubuntu Pro Realtime 22.04 LTS linux-realtime 5.15.0-1116.125 USN-8875-1
Ubuntu Pro Realtime 22.04 LTS linux-realtime-6.8 6.8.1-1056.57~22.04.2 USN-8567-1
Ubuntu Pro FIPS-updates 24.04 LTS linux-aws-fips 6.8.0-1061.64+fips1 USN-8595-3
Ubuntu Pro FIPS-updates 24.04 LTS linux-azure-fips 6.8.0-1063.71+fips2 USN-8608-1
Ubuntu Pro FIPS-updates 24.04 LTS linux-fips 6.8.0-136.136+fips2 USN-8574-2
Ubuntu Pro FIPS-updates 24.04 LTS linux-gcp-fips 6.8.0-1064.72+fips1 USN-8574-1
Ubuntu Pro FIPS-updates 22.04 LTS linux-aws-fips 5.15.0-1117.124+fips1 USN-8875-1
Ubuntu Pro FIPS-updates 22.04 LTS linux-azure-fips 5.15.0-1123.132+fips1 USN-8875-1
Ubuntu Pro FIPS-updates 22.04 LTS linux-fips 5.15.0-198.208+fips1 USN-8875-1
Ubuntu Pro FIPS-updates 22.04 LTS linux-gcp-fips 5.15.0-1118.128+fips1 USN-8877-1
Ubuntu Pro FIPS-preview 22.04 LTS linux-fips +3 No fix yet —
Ubuntu Pro 20.04 LTS linux-aws-5.15 5.15.0-1117.124~20.04.1 USN-8875-1
Ubuntu Pro 20.04 LTS linux-azure-5.15 5.15.0-1123.132~20.04.1 USN-8875-1
Ubuntu Pro 20.04 LTS linux-azure-fde-5.15 5.15.0-1122.131~20.04.1 USN-8875-1
Ubuntu Pro 20.04 LTS linux-gcp-5.15 5.15.0-1118.128~20.04.1 USN-8878-1
Ubuntu Pro 20.04 LTS linux-hwe-5.15 5.15.0-198.208~20.04.1 USN-8875-1
Ubuntu Pro 20.04 LTS linux-ibm-5.15 +1 5.15.0-1111.115~20.04.1 USN-8875-1
Ubuntu Pro 20.04 LTS linux-intel-iotg-5.15 5.15.0-1112.118~20.04.1 USN-8875-1
Ubuntu Pro 20.04 LTS linux-lowlatency-hwe-5.15 5.15.0-195.205~20.04.1 USN-8875-1
Ubuntu Pro 20.04 LTS linux-nvidia-tegra-5.15 5.15.0-1070.72~20.04.1 USN-8963-1
Ubuntu Pro 20.04 LTS linux-oracle-5.15 5.15.0-1114.120~20.04.1 USN-8879-1
ReleasePackageFixed inAdvisory
RHEL 10 rv +76 6.12.0-211.20.1.el10_2 RHSA-2026:23329
RHEL 9 rv +75 5.14.0-687.12.1.el9_8 RHSA-2026:21556
RHEL 8 kernel-rt +12 4.18.0-553.126.1.rt7.467.el8_10 RHSA-2026:21745
RHEL 8 perf +26 4.18.0-553.126.1.el8_10 RHSA-2026:21706
Show 4 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
RHEL 10.0 EUS rv +77 6.12.0-55.77.1.el10_0 RHSA-2026:24343
RHEL 9.6 EUS rv +77 5.14.0-570.119.1.el9_6 RHSA-2026:23224
RHEL 9.4 E4S bpftool 7.3.0-427.129.1.el9_4 RHSA-2026:23237
RHEL 9.4 E4S rv +62 5.14.0-427.129.1.el9_4 RHSA-2026:23237
RHEL 9.2 E4S bpftool 7.0.0-284.174.1.el9_2 RHSA-2026:22940
RHEL 9.2 E4S kernel-rt +14 5.14.0-284.174.1.rt14.459.el9_2 RHSA-2026:22900
RHEL 9.2 E4S perf +47 5.14.0-284.174.1.el9_2 RHSA-2026:22940

AlmaLinux

Errata ↗
ReleasePackageFixed inAdvisory
AlmaLinux 10 rv +74 6.12.0-211.20.1.el10_2 ALSA-2026:23329
AlmaLinux 9 rv +73 5.14.0-687.12.1.el9_8 ALSA-2026:21556
AlmaLinux 8 kernel-rt +9 4.18.0-553.126.1.rt7.467.el8_10 ALSA-2026:21745
AlmaLinux 8 perf +24 4.18.0-553.126.1.el8_10 ALSA-2026:21706

Rocky Linux

Errata ↗
ReleasePackageFixed inAdvisory
Rocky Linux 9 kernel 5.14.0-687.12.1.el9_8 RLSA-2026:21556
Rocky Linux 8 kernel 4.18.0-553.126.1.el8_10 RLSA-2026:21706
Rocky Linux 8 kernel-rt 4.18.0-553.126.1.rt7.467.el8_10 RLSA-2026:21745
ReleasePackageFixed inAdvisory
SLES 15 SP7 kernel-64kb +7 6.4.0-150700.53.90.1 SUSE-SU-2026:5091-1
SLES 15 SP7 kernel-default-base 6.4.0-150700.53.90.1.150700.17.51.1 SUSE-SU-2026:5091-1
Show 6 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
SLES for SAP 16.0 kernel-64kb +8 6.12.0-160000.41.1 SUSE-SU-2026:24662-1
SLES for SAP 16.0 kernel-default-base 6.12.0-160000.41.1.160000.2.32 SUSE-SU-2026:24662-1
SLES 16.0 kernel-64kb +8 6.12.0-160000.41.1 SUSE-SU-2026:24662-1, SUSE-SU-2026:24651-1
SLES 16.0 kernel-default-base 6.12.0-160000.41.1.160000.2.32 SUSE-SU-2026:24662-1
SLE Micro 6.2 kernel-default-base 6.12.0-160000.41.1.160000.2.32 SUSE-SU-2026:24643-1
SLE Micro 6.2 kernel-rt +5 6.12.0-160000.41.1 SUSE-SU-2026:24648-1, SUSE-SU-2026:24643-1
SLE Micro 6.1 kernel-default-base 6.4.0-159998.55.1.159998.21.41 SUSE-SU-2026:24619-1
SLE Micro 6.1 kernel-source +2 6.4.0-159998.55.1 SUSE-SU-2026:24619-1
SLE Micro 6.0 kernel-default-base 6.4.0-159998.55.1.159998.21.42 SUSE-SU-2026:24550-1
SLE Micro 6.0 kernel-source +2 6.4.0-159998.55.1 SUSE-SU-2026:24550-1
SLE Live Patching 15 SP7 kernel-default 6.4.0-150700.53.90.1 SUSE-SU-2026:5091-1
SLE Live Patching 15 SP7 kernel-livepatch-SLE15-SP7_Update_24 1-150700.15.3.1 SUSE-SU-2026:5091-1
ReleasePackageFixed inAdvisory
openSUSE Tumbleweed kernel-source 7.0.7-1.1 openSUSE-SU-2026:10793-1

Amazon Linux

ReleasePackageFixed inAdvisory
Amazon Linux 2023 kernel-livepatch-6.18.35-68.127 +3 1:1.0-0.amzn2023 ALAS2023-2026-1924, ALAS2023-2026-1881, ALAS2023-2026-1816
Amazon Linux 2023 perf +11 1:6.1.176-220.358.amzn2023 ALAS2023-2026-1924
Amazon Linux 2023 perf6.12 +11 1:6.12.88-119.157.amzn2023 ALAS2023-2026-1816, ALAS2023-2026-1753
Amazon Linux 2023 perf6.18 +12 1:6.18.35-68.127.amzn2023 ALAS2023-2026-1881

Azure Linux

ReleasePackageFixed inAdvisory
Azure Linux 3 kernel 6.6.141.1-1 —

Oracle Linux

ReleasePackageFixed inAdvisory
Oracle Linux 10 rv +29 6.12.0-211.34.1.el10_2 ELSA-2026-23329
Oracle Linux 9 kernel-uek +34 6.12.0-204.92.4.2.el10uek ELSA-2026-50372
Oracle Linux 9 rv +28 5.14.0-687.17.1.el9_8 ELSA-2026-21556
Oracle Linux 8 perf +19 4.18.0-553.126.1.el8_10 ELSA-2026-21706

Advisories 50

References