CVE-2026-64390
Received Received - Intake

BaseFortify

Publication date: 2026-07-25

Last updated on: 2026-07-25

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: track the connection owning a byte-range lock SMB2_LOCK adds each granted byte-range lock to both the file lock list and the lock list of the connection which handled the request. The final close and durable handle paths, however, remove the connection list entry while holding fp->conn->llist_lock. With SMB3 multichannel, the connection handling the LOCK request can be different from the connection which opened the file. The entry can therefore be removed under a different spinlock from the one protecting the list it belongs to. A concurrent traversal can then access freed struct ksmbd_lock and struct file_lock objects. Record the connection owning each lock's clist entry and hold a reference to it while the entry is linked. Use that connection and its llist_lock for unlock, rollback, close, and durable preserve. Durable reconnect assigns the new connection as the owner when publishing the locks again.

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Meta Information

Published
2026-07-25
Last Modified
2026-07-25
Generated
2026-07-25
AI Q&A
2026-07-25
EPSS Evaluated
N/A
NVD
CVE-2026-64390
EUVD
EUVD-2026-48934

Affected Vendors & Products

Currently, no data is known.

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Exploitability

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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a race condition in the ksmbd SMB server implementation. When handling SMB2_LOCK requests, byte-range locks are added to both a file lock list and a connection lock list. However, during final close or durable handle operations, the connection list entry is removed while holding a spinlock. With SMB3 multichannel, the connection handling the lock request may differ from the one that opened the file, leading to a situation where a lock entry is removed under a different spinlock than the one protecting its list. This can cause a concurrent traversal to access freed memory, resulting in use-after-free vulnerabilities affecting struct ksmbd_lock and struct file_lock objects.

The fix involves tracking the connection owning each lock's clist entry and holding a reference to it while the entry is linked. The correct connection and its spinlock are then used for unlock, rollback, close, and durable preserve operations. Durable reconnect assigns the new connection as the owner when republishing locks.

Impact Analysis

This vulnerability could allow an attacker to cause a denial of service by crashing the system or to potentially execute arbitrary code with kernel privileges. If exploited, it may lead to system instability, data corruption, or unauthorized access to sensitive information. Systems using the ksmbd SMB server with SMB3 multichannel enabled are particularly at risk.

Mitigation Strategies

Update the Linux kernel to the latest patched version to resolve the ksmbd byte-range lock vulnerability. Monitor SMB2_LOCK operations and ensure multichannel connections are handled correctly to prevent concurrent access issues.

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