Out-of-bounds read in Linux kernel - CVE-2026-68388
Published: August 12, 2026
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
Vulnerability details
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.
Affected software
Linux kernel
Red Hat Enterprise Linux for Real Time
Red Hat Enterprise Linux for Real Time for NFV
kernel-rt (Red Hat package)
Red Hat Enterprise Linux for Real Time
Red Hat Enterprise Linux for Real Time for NFV
kernel-rt (Red Hat package)
How to mitigate CVE-2026-68388
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
kernel-rt (Red Hat package) - update to 4.18.0-553.157.1.rt7.498.el8_10
External References
- 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