Linux Kernel up to 6.4.6 SMB Client cifs_smb_ses_inc_refcount use after free

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.4.6. It has been classified as critical. This impacts the function cifs_smb_ses_inc_refcount of the component SMB Client. This manipulation causes use after free. This vulnerability is handled as CVE-2023-54076. There is not any exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as critical was found in Linux Kernel up to 6.4.6. Affected by this vulnerability is the function cifs_smb_ses_inc_refcount of the component SMB Client. The manipulation with an unknown input leads to a use after free vulnerability. The CWE definition for the vulnerability is CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. 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: smb: client: fix missed ses refcounting Use new cifs_smb_ses_inc_refcount() helper to get an active reference of @ses and @ses->dfs_root_ses (if set). This will prevent @ses->dfs_root_ses of being put in the next call to cifs_put_smb_ses() and thus potentially causing an use-after-free bug.

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2023-54076 since 12/24/2025. The exploitation appears to be easy. 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 01/02/2026).

The vulnerability scanner Nessus provides a plugin with the ID 279864 (Linux Distros Unpatched Vulnerability : CVE-2023-54076), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.4.7 eliminates this vulnerability. Applying the patch eb382196e6f6e05cfafdab797840e5a96c6e7bf0/bf99f6be2d20146942bce6f9e90a0ceef12cbc1e is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (279864) and CERT Bund (WID-SEC-2025-2929). Be aware that VulDB is the high quality source for vulnerability data.

Affected

• Open Source Linux Kernel

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.4.0
• 6.4.1
• 6.4.2
• 6.4.3
• 6.4.4
• 6.4.5
• 6.4.6

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Be aware that VulDB is the high quality source for vulnerability data.

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