Out-of-bounds read in Linux kernel - CVE-2026-68388

Vulnerability identifier: #VU141656

CSH Severity: Low

CVSS v4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-68388

CWE-ID: CWE-125

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to cause a denial of service.

The vulnerability exists due to an out-of-bounds read in smb3_simple_fallocate_range() when handling server-reported allocated ranges during fallocate operations. A local user can trigger fallocate on an SMB client mount backed by a server that returns overlapping or malformed allocated ranges to cause a denial of service.

A later write to a skipped hole may fail with ENOSPC.

Linux kernel
Red Hat Enterprise Linux for Real Time
Red Hat Enterprise Linux for Real Time for NFV
Anolis OS
Ubuntu
kernel-rt (Red Hat package)
bpftool
kernel-doc
kernel-abi-stablelists
python3-perf
perf
kernel-tools-libs-devel
kernel-tools-libs
kernel-tools
kernel-modules-extra
kernel-modules
kernel-headers
kernel-devel
kernel-debug-modules-extra
kernel-debug-modules
kernel-debug-devel
kernel-debug-core
kernel-debug
kernel-cross-headers
kernel-core
kernel
linux-nvidia-tegra (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
kernel-rt (Red Hat package) - update to 4.18.0-553.157.1.rt7.498.el8_10
bpftool - update to 4.18.0-553.157.1.0.1
kernel-doc - update to 4.18.0-553.157.1.0.1
kernel-abi-stablelists - update to 4.18.0-553.157.1.0.1
python3-perf - update to 4.18.0-553.157.1.0.1
perf - update to 4.18.0-553.157.1.0.1
kernel-tools-libs-devel - update to 4.18.0-553.157.1.0.1
kernel-tools-libs - update to 4.18.0-553.157.1.0.1
kernel-tools - update to 4.18.0-553.157.1.0.1
kernel-modules-extra - update to 4.18.0-553.157.1.0.1
kernel-modules - update to 4.18.0-553.157.1.0.1
kernel-headers - update to 4.18.0-553.157.1.0.1
kernel-devel - update to 4.18.0-553.157.1.0.1
kernel-debug-modules-extra - update to 4.18.0-553.157.1.0.1
kernel-debug-modules - update to 4.18.0-553.157.1.0.1
kernel-debug-devel - update to 4.18.0-553.157.1.0.1
kernel-debug-core - update to 4.18.0-553.157.1.0.1
kernel-debug - update to 4.18.0-553.157.1.0.1
kernel-cross-headers - update to 4.18.0-553.157.1.0.1
kernel-core - update to 4.18.0-553.157.1.0.1
kernel - update to 4.18.0-553.157.1.0.1
linux-nvidia-tegra (Ubuntu package) - update to 6.8.0-1035.38

• https://git.kernel.org/stable/c/377fe3e583e46369ee1004d5cfe12271d6589a68
• https://git.kernel.org/stable/c/437637f5ff3f573b2edf8571de91fb00a21eb4e6
• https://git.kernel.org/stable/c/7e08ab7a061b17ac1989a225c6afb53f44a86808
• https://git.kernel.org/stable/c/a4a09e5142835633fffbde68bd0a039ba4d4bf97
• https://git.kernel.org/stable/c/b09ae45d85dc816987a71db9eebc54b0ae288e94

• Out-of-bounds read in Linux kernel smb client
• Red Hat Enterprise Linux 8 update for kernel-rt
• Anolis OS update for kernel:4.18
• Ubuntu update for linux-nvidia-tegra