Linux Kernel up to 7.2.5 ksmbd vfs_lock_file conn null pointer dereference

Summaryinfo

A vulnerability has been found in Linux Kernel up to 7.2.5 and classified as critical. This affects the function vfs_lock_file of the component ksmbd. The manipulation of the argument conn leads to null pointer dereference. This vulnerability is documented as CVE-2026-90156. The attack can be initiated remotely. There is not any exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.5 and classified as critical. This issue affects the function vfs_lock_file of the component ksmbd. The manipulation of the argument conn with an unknown input leads to a null pointer dereference vulnerability. Using CWE to declare the problem leads to CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. Impacted is availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: ksmbd: safely discard unregistered deferred locks When vfs_lock_file() defers a lock, smb2_lock() puts its ksmbd_lock on rollback_list before allocating and registering the asynchronous work. If either operation fails, rollback assumes that smb_lock->conn is initialized and dereferences NULL. The deferred file_lock also remains linked into the VFS blocked-lock state while it is freed. Keep the lock off rollback_list until async setup succeeds. On setup failures, explicitly unblock and wake the deferred lock before freeing it and its ksmbd wrapper.

The advisory is shared at git.kernel.org. The identification of this vulnerability is CVE-2026-90156 since 09/11/2026. The exploitation is known to be easy. The attack may be initiated 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 d09af9a35ff7b77a950b507133d9092aadbfeff4/054bcca4cd9f00719b01f7108b51a2168fb94f15 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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