Linux Kernel up to 6.17.7 time_deleg state issue

Summaryinfo

A vulnerability described as critical has been identified in Linux Kernel up to 6.17.7. Affected by this vulnerability is the function time_deleg. The manipulation results in state issue. This vulnerability is reported as CVE-2025-40326. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.17.7. It has been classified as critical. Affected is the function time_deleg. The manipulation with an unknown input leads to a state issue vulnerability. CWE is classifying the issue as CWE-371. The impact remains unknown. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: NFSD: Define actions for the new time_deleg FATTR4 attributes NFSv4 clients won't send legitimate GETATTR requests for these new attributes because they are intended to be used only with CB_GETATTR and SETATTR. But NFSD has to do something besides crashing if it ever sees a GETATTR request that queries these attributes. RFC 8881 Section 18.7.3 states: > The server MUST return a value for each attribute that the client > requests if the attribute is supported by the server for the > target file system. If the server does not support a particular > attribute on the target file system, then it MUST NOT return the > attribute value and MUST NOT set the attribute bit in the result > bitmap. The server MUST return an error if it supports an > attribute on the target but cannot obtain its value. In that case, > no attribute values will be returned. Further, RFC 9754 Section 5 states: > These new attributes are invalid to be used with GETATTR, VERIFY, > and NVERIFY, and they can only be used with CB_GETATTR and SETATTR > by a client holding an appropriate delegation. Thus there does not appear to be a specific server response mandated by specification. Taking the guidance that querying these attributes via GETATTR is "invalid", NFSD will return nfserr_inval, failing the request entirely.

The advisory is shared for download at git.kernel.org. This vulnerability is traded as CVE-2025-40326 since 04/16/2025. 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 02/23/2026).

The vulnerability scanner Nessus provides a plugin with the ID 278685 (Linux Distros Unpatched Vulnerability : CVE-2025-40326), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.17.8 eliminates this vulnerability. Applying the patch d8f3f94dc950e7c62c96af432c26745885b0a18a/4f76435fd517981f01608678c06ad9718a86ee98 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 (278685) and CERT Bund (WID-SEC-2025-2756). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Affected

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

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.17.0
• 6.17.1
• 6.17.2
• 6.17.3
• 6.17.4
• 6.17.5
• 6.17.6
• 6.17.7

License

• open-source

Website

• Vendor: https://www.kernel.org/

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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