Linux Kernel up to 7.2.5 NFSv4 Callback Decoding decode_cb_sequence_args uninitialized variable

Summaryinfo

A vulnerability was found in Linux Kernel up to 7.2.5. It has been declared as very critical. This issue affects the function decode_cb_sequence_args of the component NFSv4 Callback Decoding. The manipulation results in uninitialized variable. This vulnerability was named CVE-2026-90104. The attack may be performed from remote. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.5. It has been classified as very critical. Affected is the function decode_cb_sequence_args of the component NFSv4 Callback Decoding. The manipulation with an unknown input leads to a uninitialized variable vulnerability. CWE is classifying the issue as CWE-457. The code uses a variable that has not been initialized, leading to unpredictable or unintended results. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: NFSv4.1: zero referring call lists before decoding decode_cb_sequence_args() allocates csa_rclists with kmalloc_objs(), so each referring_call_list starts uninitialized. decode_rc_list() assigns rcl_refcalls only when rcl_nrefcalls is nonzero. A valid list with zero referring calls therefore leaves the pointer uninitialized, and nfs4_callback_sequence() later passes stale slab contents to kfree(). Allocate csa_rclists with kzalloc_objs() so every rcl_refcalls member is NULL from the beginning, including valid empty referring call lists.

The advisory is shared for download at git.kernel.org. This vulnerability is traded as CVE-2026-90104 since 09/11/2026. The exploitability is told to be easy. It is possible to launch the attack 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 09/17/2026).

Upgrading to version 7.2.6 or 7.3-rc1 eliminates this vulnerability. Applying the patch f31f3c042e024aef437cda42f0424ae8d4594b6c/8fa4804fe62ca4155a2d8fc2789d630376cbf2fc 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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