CVE-2026-93829

Received Received - Intake

Race Condition in Linux Kernel SMB Client

Publication date: 2026-09-24

Last updated on: 2026-10-03

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix races in cifsd thread creation The cifsd demultiplex thread can run and access tcp_ses before the parent thread has finished populating tcp_ses, which the worker thread accesses locklessly. Also, the kthread_run macro may start the thread before returning the thread pointer. Because the pointer is part of the structure that the thread can access, if the kernel is preempted after the thread is spawned, but before the thread pointer is populated and the thread attempts to exit, it will sleep, waiting for a SIGKILL signal. Fix this by moving creation of the thread to after all of tcp_ses'es fields are populated, and spawning the thread last, using a split kthread_create/wake_up_process logic.

CVSS Scores

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Meta Information

Published

2026-09-24

Last Modified

2026-10-03

Generated

2026-10-15

AI Q&A

2026-09-24

EPSS Evaluated

2026-10-13

NVD

CVE-2026-93829

EUVD

EUVD-2026-86218

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This is a race condition in the Linux kernel's SMB client (cifsd). The vulnerability occurs when the cifsd demultiplex thread starts running and accesses tcp_ses before the parent thread has fully initialized it. Additionally, the kthread_run macro may start the thread before returning its pointer, leading to a situation where the thread could sleep indefinitely waiting for a SIGKILL signal if preempted during initialization.

Detection Guidance

This vulnerability is specific to the Linux kernel's cifsd (SMB server) implementation and involves race conditions in thread creation. Detection requires checking kernel logs for cifsd-related errors or crashes, particularly around thread initialization. Commands like dmesg | grep cifsd or journalctl -k | grep cifsd may help identify issues.

Impact Analysis

This vulnerability could cause system instability or crashes due to race conditions in thread creation. It may lead to unexpected behavior in SMB client operations, potentially disrupting file sharing or network services that rely on the cifsd component.

Compliance Impact

This vulnerability affects Linux kernel SMB client functionality but does not directly impact compliance with GDPR, HIPAA, or similar standards. The issue involves race conditions in thread creation for the cifsd component, which could lead to system instability or crashes but does not involve data exposure or unauthorized access that would typically trigger regulatory violations.

Mitigation Strategies

Update your Linux kernel to the latest patched version that includes the fix for this vulnerability. If using a distribution kernel, apply vendor-provided updates immediately. Avoid using the cifsd (SMB server) feature until patched, or disable it if not required.

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