CVE-2026-80926

Received Received - Intake

Use-After-Free in Linux Kernel ksmbd

Publication date: 2026-09-11

Last updated on: 2026-09-11

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in oplock break notification smb2_oplock_break_noti() reads opinfo->conn without any lock and dereferences it after two allocations which may sleep. When the durable handle owning the oplock is disconnected, session_fd_check() clears opinfo->conn and drops its conn reference under ci->m_lock, and the last ksmbd_conn_put() frees the connection. A break triggered by another connection that races with the teardown can then resurrect the freed connection: ksmbd_conn_get() is a plain atomic_inc, and the queued break work later dereferences the stale conn via ksmbd_conn_write(), a use-after-free reachable by any authenticated client holding a durable batch oplock. Thread the caller's inode into the notification path instead of taking a new reference on it. Every caller of oplock_break() already holds a live ksmbd_file (or an explicit ksmbd_inode_lookup_lock() reference, in the parent lease break paths) on the inode that owns the break target's oplock list, so ci cannot be freed during the call, and its lock can be taken without dereferencing opinfo->o_fp, which a concurrent close may free. Select and pin the connection under ci->m_lock, the same lock session_fd_check() and ksmbd_reopen_durable_fd() use to update opinfo->conn, so a concurrent detach either loses the race to the clear or keeps the connection alive until the notification work releases it. Transfer the reference to the work item and release it on allocation failures.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-09-11

Last Modified

2026-09-11

Generated

2026-09-12

AI Q&A

2026-09-12

EPSS Evaluated

N/A

NVD

CVE-2026-80926

EUVD

EUVD-2026-76248

Affected Vendors & Products

Currently, no data is known.

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 the smb2_oplock_break_noti() function accesses a connection pointer without proper locking, leading to a situation where a freed memory location might be accessed later. This happens due to a race condition between connection teardown and oplock break notifications.

Detection Guidance

This vulnerability involves a use-after-free in the ksmbd kernel module related to SMB oplock breaks. Detection requires checking for kernel logs or system crashes related to ksmbd operations. Monitor logs for ksmbd-related errors or segfaults. No specific commands are provided in the context.

Impact Analysis

An authenticated attacker could exploit this to cause a denial of service or potentially execute arbitrary code with kernel privileges. The vulnerability is reachable by any client holding a durable batch oplock, making it a serious security risk for systems running vulnerable ksmbd versions.

Mitigation Strategies

Apply the Linux kernel patch that resolves this issue. Disable the ksmbd module if not in use. Update SMB server configurations to avoid durable batch oplocks if possible. Monitor for signs of exploitation or system instability.

Hi! I’m here to help you understand CVE-2026-80926. Ask me anything about the vulnerability, its impact, or mitigation strategies.

0/70