Linux Kernel up to 7.2.5 ksmbd ksmbd_free_work_struct improper synchronization

Summaryinfo

A vulnerability was found in Linux Kernel up to 7.2.5. It has been rated as very critical. Affected by this issue is the function ksmbd_free_work_struct of the component ksmbd. This manipulation causes improper synchronization. This vulnerability appears as CVE-2026-90168. The attack may be initiated remotely. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as very critical was found in Linux Kernel up to 7.2.5. Affected by this vulnerability is the function ksmbd_free_work_struct of the component ksmbd. The manipulation with an unknown input leads to a improper synchronization vulnerability. The CWE definition for the vulnerability is CWE-662. The product utilizes multiple threads or processes to allow temporary access to a shared resource that can only be exclusive to one process at a time, but it does not properly synchronize these actions, which might cause simultaneous accesses of this resource by multiple threads or processes. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: ksmbd: retain connection for pending notify work Deferred CHANGE_NOTIFY work keeps an async message ID after the original request work is released. A durable handle can outlive its connection, so the connection teardown can destroy its async IDA before the handle close releases the pending notify work. Give the synthetic deferred work a connection reference. Release it after the async ID in ksmbd_free_work_struct(). This keeps the async IDA alive until the deferred work is released, even when the original connection has already left the connection list. During server shutdown there is no client to receive a cleanup response. Skip the write and only release the pending work.

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2026-90168 since 09/11/2026. The exploitation appears to be easy. The attack can be launched remotely. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/17/2026).

Upgrading to version 7.2.6 or 7.3-rc1 eliminates this vulnerability. Applying the patch 50be5e96c381ae995b7de3869eecdc84476be7f2/f495154703cbcc0050cfd53469bd56965791616b is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5

License

• open-source

Website

• Vendor: https://www.kernel.org/

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