CVE-2026-89683

Received Received - Intake

Linux kernel NFS V4ROOT export dentry reference leak

Publication date: 2026-09-11

Last updated on: 2026-09-11

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: fix dentry ref leak on V4ROOT export filehandle lookup nfsd_set_fh_dentry() leaks the dentry reference from exportfs_decode_fh_raw() when the NFS3_FHSIZE or NFS_FHSIZE switch cases detect NFSEXP_V4ROOT and goto out. The out: label calls exp_put() but never dput(dentry), and fhp->fh_dentry was never assigned so fh_put() cannot compensate. A crafted NFSv3 filehandle targeting a V4ROOT export's fsid triggers the leak on every request.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-09-11

Last Modified

2026-09-11

Generated

2026-09-12

AI Q&A

2026-09-12

EPSS Evaluated

N/A

NVD

CVE-2026-89683

EUVD

EUVD-2026-76595

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This is a dentry reference leak in the Linux kernel's NFS server (nfsd). When handling a crafted NFSv3 filehandle targeting a V4ROOT export's fsid, the kernel fails to release a dentry reference properly. This happens because nfsd_set_fh_dentry() does not call dput(dentry) when detecting NFSEXP_V4ROOT in certain switch cases, leading to a memory leak on every request.

Detection Guidance

This vulnerability involves a dentry reference leak in the Linux kernel's NFS server when handling crafted NFSv3 filehandles targeting a V4ROOT export. Detection requires checking for unusual dentry reference counts or NFS server crashes. Monitor kernel logs for NFS-related errors or use tools like 'dmesg' or 'journalctl -k' to inspect kernel messages for NFS-related issues.

Impact Analysis

The vulnerability could cause memory exhaustion on systems running vulnerable NFS servers. Over time, this may lead to performance degradation, system instability, or crashes due to running out of available memory for dentry objects.

Mitigation Strategies

Apply the latest Linux kernel patches that address this issue. If immediate patching is not possible, consider disabling NFSv3 exports or restricting access to V4ROOT exports until the patch is applied. Monitor NFS server performance and logs for signs of exploitation.

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