Linux Kernel up to 7.3.1 ksmbd proc_remove race condition

Summaryinfo

A vulnerability classified as very critical was found in Linux Kernel up to 7.3.1. This impacts the function proc_remove of the component ksmbd. Executing a manipulation can lead to race condition. This vulnerability appears as CVE-2026-99280. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.3.1. It has been declared as very critical. This vulnerability affects the function proc_remove of the component ksmbd. The manipulation with an unknown input leads to a race condition vulnerability. The CWE definition for the vulnerability is CWE-362. The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: ksmbd: drain session procfs readers before dropping table references Session registration failure and connection cleanup can drop the table reference while the per-session procfs entry is still accessible. If a reader holds the last remaining reference, its final put calls proc_remove() from its own callback and waits for that callback to finish. Remove the procfs entry before dropping the table reference in the registration failure path. Queue sessions removed during connection cleanup and drain their procfs readers after releasing both session locks, then return their table references. Keep the global hash node unhashed while a session is queued so a concurrent unregister cannot drop the reference again. Previous-session replacement also destroys the file table before the session is finally freed. Detach the idr under the lock used by procfs file counters, and report zero files after it has been detached. This prevents a reader from accessing the idr during or after its destruction.

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2026-99280 since 09/25/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 11/07/2026).

Upgrading to version 7.3.2 or 7.4-rc1 eliminates this vulnerability. Applying the patch 6789f0983f8e85ce3a5ed8c50fc05d613ead9c2c/1c087cf7d5386c708d8984b263280b42b3daada0 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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