Linux Kernel up to 7.2.3 nfsd nfsd_file_do_acquire input validation

Summaryinfo

A vulnerability identified as very critical has been detected in Linux Kernel up to 7.2.3. This affects the function nfsd_file_do_acquire of the component nfsd. The manipulation leads to input validation. This vulnerability is documented as CVE-2026-89687. The attack can be initiated remotely. There is not any exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.3 and classified as very critical. This issue affects the function nfsd_file_do_acquire of the component nfsd. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: nfsd: ensure nfsd_file_do_acquire() does not use a non-opened file ->atomic_open is permitted to return success without actually opening the file. It indicates this by calling finish_no_open(). This means dentry_create() can return a file which hasn't been opened. This is extremely unlikely as ->atomic_open handlers typically use finish_no_open() only for already existing files, and dentry_create() isn't called in that case, and the parent being locked should prevent races. However out of an abundance of caution it seems wise to teach nfsd to only use the file returned by dentry_create() if FMODE_OPENED is set, indicating that it has in fact been opened.

It is possible to read the advisory at git.kernel.org. The identification of this vulnerability is CVE-2026-89687 since 09/11/2026. The exploitation is known to be easy. The attack may be initiated remotely. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 09/12/2026).

Upgrading to version 7.2.4 or 7.3-rc1 eliminates this vulnerability. Applying the patch a95a1cffacd0203100297001719160160f443dd6/5859cc01fee06a2cd7458905a9593082fbab06e1 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

License

• open-source

Website

• Vendor: https://www.kernel.org/

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