Linux Kernel up to 7.3.1 ksmbd destroy_previous_session locking

Summaryinfo

A vulnerability classified as critical has been found in Linux Kernel up to 7.3.1. This affects the function destroy_previous_session of the component ksmbd. Performing a manipulation results in locking. This vulnerability is reported as CVE-2026-99276. The attack is possible to be carried out remotely. No exploit exists. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.3.1. It has been classified as critical. This affects the function destroy_previous_session of the component ksmbd. The manipulation with an unknown input leads to a locking vulnerability. CWE is classifying the issue as CWE-667. The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors. This is going to have an impact on availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: ksmbd: defer connection scavenging while session locks are busy The expiration worker holds conn_list_lock for reading while checking for authenticated sessions. Without this change, the check can wait for conn->session_lock or sessions_table_lock. In destroy_previous_session(), the status updates after ksmbd_conn_wait_idle_sess() run with both session locks held for writing. Both the KSMBD_SESS_GOOD error path and the KSMBD_SESS_NEED_SETUP success path call ksmbd_all_conn_set_status(), which takes conn_list_lock for reading. A writer queued on conn_list_lock can block these new read acquisitions. The worker then waits for a session lock held by destroy_previous_session(), which waits behind the writer. The writer cannot proceed until the worker releases conn_list_lock. Try both session locks instead of waiting in the scavenging check. Keep the connection when either lock is busy and let the periodic worker retry later.

It is possible to read the advisory at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-99276 since 09/25/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 11/07/2026).

Upgrading to version 7.3.2 or 7.4-rc1 eliminates this vulnerability. Applying the patch 4e4e8b38994a0b0fc23f00ca6698b469a41abe70/b4bae7af1154089be87c7475218264fcbfd16d10 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

• 7.3.0
• 7.3.1

License

• open-source

Website

• Vendor: https://www.kernel.org/

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