CVE-2026-72381

Received Received - Intake

ksmbd Use-After-Free in Durable Handle Owner Check

Publication date: 2026-08-15

Last updated on: 2026-08-17

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free of fp->owner.name in durable handle owner check Two concurrent SMB2 durable reconnects (DH2C/DHnC) on the same persistent_id race the fp->owner.name compare-read in ksmbd_vfs_compare_durable_owner() against the kfree() in ksmbd_reopen_durable_fd()'s reopen-success path. fp->owner.name is a standalone kstrdup() buffer whose lifetime is independent of the fp refcount, and the two sites share no lock: the compare reads the buffer while the reopen frees it, so the strcmp() can dereference freed memory. Commit 7ce4fc40018d ("ksmbd: fix durable reconnect double-bind race in ksmbd_reopen_durable_fd") made the fp->conn claim atomic under global_ft.lock (closing the owner.name double-free and the ksmbd_file write-UAF), but the compare-read versus reopen-free pair was left unserialized. BUG: KASAN: slab-use-after-free in strcmp+0x2c/0x80 Read of size 1 by task kworker strcmp ksmbd_vfs_compare_durable_owner smb2_check_durable_oplock smb2_open Freed by task kworker: kfree ksmbd_reopen_durable_fd smb2_open Allocated by task kworker: kstrdup session_fd_check smb2_session_logoff The buggy address belongs to the cache kmalloc-8 Serialize both sides of the race with fp->f_lock. The global durable file-table lock still protects the durable reconnect claim, but fp->owner.name is per-open state and does not need to block unrelated durable table lookups or reconnects. The teardown is left at its existing location after the reopen-success point so that an __open_id() rollback still retains owner.name for a later legitimate reconnect to verify.

CVSS Scores

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Meta Information

Published

2026-08-15

Last Modified

2026-08-17

Generated

2026-09-04

AI Q&A

2026-08-15

EPSS Evaluated

2026-09-03

NVD

CVE-2026-72381

EUVD

EUVD-2026-59280

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 use-after-free vulnerability in the Linux kernel's ksmbd module. It occurs when two concurrent SMB2 durable reconnects race to access the same file's owner.name field. One process may free the memory while another is still reading it, leading to a slab-use-after-free error in strcmp.

Detection Guidance

This vulnerability is specific to the Linux kernel's ksmbd implementation and involves a use-after-free condition during SMB2 durable reconnects. Detection requires checking kernel logs for KASAN reports or slab-use-after-free errors related to strcmp in ksmbd_vfs_compare_durable_owner. Monitor logs for crashes or memory corruption events during SMB operations.

Impact Analysis

This could allow an attacker to cause a kernel crash or execute arbitrary code with kernel privileges by exploiting the race condition. It may lead to denial-of-service or potential privilege escalation on systems using ksmbd for SMB file sharing.

Compliance Impact

This vulnerability is a use-after-free flaw in the Linux kernel's ksmbd SMB server implementation. It does not directly impact compliance with standards like GDPR or HIPAA, as those focus on data protection, access controls, and privacy. However, if exploited, it could lead to unauthorized access or data corruption, which may indirectly affect compliance by compromising data integrity or confidentiality.

Mitigation Strategies

Apply the kernel patch that fixes the race condition in ksmbd durable reconnect handling. Update to a Linux kernel version that includes the fix for CVE-2026-72381. If immediate patching is not possible, disable the ksmbd service or restrict SMB2 durable reconnect functionality until the patch is applied.

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