Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-11-07T14:08:47 kernel: kernel: Denial of Service via improper session cleanup in ksmbd 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CWE-833

In the Linux kernel, the following vulnerability has been resolved: ksmbd: drain session procfs readers before dropping table references Session registration failure and connection cleanup can drop the table reference while the per-session procfs entry is still accessible. If a reader holds the last remaining reference, its final put calls proc_remove() from its own callback and waits for that callback to finish. Remove the procfs entry before dropping the table reference in the registration failure path. Queue sessions removed during connection cleanup and drain their procfs readers after releasing both session locks, then return their table references. Keep the global hash node unhashed while a session is queued so a concurrent unregister cannot drop the reference again. Previous-session replacement also destroys the file table before the session is finally freed. Detach the idr under the lock used by procfs file counters, and report zero files after it has been detached. This prevents a reader from accessing the idr during or after its destruction.

A flaw was found in the Linux kernel's ksmbd. Session registration failures and connection cleanups can drop internal session references while the per-session procfs (process information pseudo-filesystem) entry is still accessible. A local user reading these entries during concurrent session teardown can trigger a deadlock or memory corruption, resulting in a Denial of Service (DoS).

This vulnerability is rated as having Moderate severity for Red Hat because successful exploitation requires local authenticated access and results exclusively in a denial of service without impacting confidentiality or integrity. By default, Red Hat Enterprise Linux utilizes Samba as the supported userspace SMB solution and does not enable the in-kernel ksmbd server. Consequently, systems operating with default configurations are not exposed unless ksmbd has been explicitly loaded and configured. To mitigate this vulnerability, prevent the ksmbd kernel module from being loaded: 1. Create a configuration file to disable the module: echo "install ksmbd /bin/true" > /etc/modprobe.d/ksmbd.conf 2. If the module is already loaded, unload it: modprobe -r ksmbd Caveat: Disabling this module prevents the system from running the in-kernel SMB server. Warning: If the module is currently in use, unloading it will disrupt active SMB connections. A system restart may be required if the module cannot be unloaded dynamically. Red Hat Enterprise Linux 10 Not affected kernel Red Hat Enterprise Linux 6 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel-rt Red Hat Enterprise Linux 8 Not affected kernel Red Hat Enterprise Linux 8 Not affected kernel-rt Red Hat Enterprise Linux 9 Not affected kernel Red Hat Enterprise Linux 9 Not affected kernel-rt Red Hat OpenShift Container Platform 4 Not affected openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 4 Not affected openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 Not affected openshift/ose-rhel-coreos-10 Red Hat OpenShift Container Platform 5 Not affected openshift/ose-rhel-coreos-9 https://www.cve.org/CVERecord?id=CVE-2026-99280 https://nvd.nist.gov/vuln/detail/CVE-2026-99280 https://git.kernel.org/stable/c/1c087cf7d5386c708d8984b263280b42b3daada0 https://git.kernel.org/stable/c/6789f0983f8e85ce3a5ed8c50fc05d613ead9c2c