Linux Kernel up to 6.18.24/7.0.1 ksmbd ksmbd_vfs_compare_durable_owner comparison

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.18.24/7.0.1. It has been classified as critical. Affected by this issue is the function ksmbd_vfs_compare_durable_owner of the component ksmbd. Performing a manipulation results in comparison. This vulnerability was named CVE-2026-31717. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as critical has been found in Linux Kernel up to 6.18.24/7.0.1. This affects the function ksmbd_vfs_compare_durable_owner of the component ksmbd. The manipulation with an unknown input leads to a comparison vulnerability. CWE is classifying the issue as CWE-697. The product compares two entities in a security-relevant context, but the comparison is incorrect, which may lead to resultant weaknesses. The impact remains unknown. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate owner of durable handle on reconnect Currently, ksmbd does not verify if the user attempting to reconnect to a durable handle is the same user who originally opened the file. This allows any authenticated user to hijack an orphaned durable handle by predicting or brute-forcing the persistent ID. According to MS-SMB2, the server MUST verify that the SecurityContext of the reconnect request matches the SecurityContext associated with the existing open. Add a durable_owner structure to ksmbd_file to store the original opener's UID, GID, and account name. and catpure the owner information when a file handle becomes orphaned. and implementing ksmbd_vfs_compare_durable_owner() to validate the identity of the requester during SMB2_CREATE (DHnC).

It is possible to read the advisory at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-31717 since 03/09/2026. The exploitability is told 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 06/30/2026).

The vulnerability scanner Nessus provides a plugin with the ID 321868 (Debian dsa-6355 : ata-modules-6.12.90+deb13-armmp-di - security update), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.18.25, 7.0.2 or 7.1-rc1 eliminates this vulnerability. Applying the patch 00ce8d6789dae72d042a4522264964c72891ca37/c908c853f304a4969b5aa10eba0b50350cc65b80/49110a8ce654bbe56bef7c5e44cce31f4b102b8a 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 (321868) and CERT Bund (WID-SEC-2026-1346). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

• Google Container-Optimized OS
• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• Open Source Linux Kernel
• RESF Rocky Linux
• Microsoft Azure Linux
• Red Hat OpenShift

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9
• 6.18.10
• 6.18.11
• 6.18.12
• 6.18.13
• 6.18.14
• 6.18.15
• 6.18.16
• 6.18.17
• 6.18.18
• 6.18.19
• 6.18.20
• 6.18.21
• 6.18.22
• 6.18.23
• 6.18.24
• 7.0.0
• 7.0.1

License

• open-source

Website

• Vendor: https://www.kernel.org/

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