In the Linux kernel, the following vulnerability has been resolved:

nfsd: fix refcount leak in nfsd_set_fh_dentry()

nfsd exports a "pseudo root filesystem" which is used by NFSv4 to find
the various exported filesystems using LOOKUP requests from a known root
filehandle. NFSv3 uses the MOUNT protocol to find those exported
filesystems and so is not given access to the pseudo root filesystem.

If a v3 (or v2) client uses a filehandle from that filesystem,
nfsd_set_fh_dentry() will report an error, but still stores the export
in "struct svc_fh" even though it also drops the reference (exp_put()).
This means that when fh_put() is called an extra reference will be dropped
which can lead to use-after-free and possible denial of service.

Normal NFS usage will not provide a pseudo-root filehandle to a v3
client. This bug can only be triggered by the client synthesising an
incorrect filehandle.

To fix this we move the assignments to the svc_fh later, after all
possible error cases have been detected.
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Tue, 25 Nov 2025 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

threat_severity

Important


Mon, 24 Nov 2025 13:15:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: nfsd: fix refcount leak in nfsd_set_fh_dentry() nfsd exports a "pseudo root filesystem" which is used by NFSv4 to find the various exported filesystems using LOOKUP requests from a known root filehandle. NFSv3 uses the MOUNT protocol to find those exported filesystems and so is not given access to the pseudo root filesystem. If a v3 (or v2) client uses a filehandle from that filesystem, nfsd_set_fh_dentry() will report an error, but still stores the export in "struct svc_fh" even though it also drops the reference (exp_put()). This means that when fh_put() is called an extra reference will be dropped which can lead to use-after-free and possible denial of service. Normal NFS usage will not provide a pseudo-root filehandle to a v3 client. This bug can only be triggered by the client synthesising an incorrect filehandle. To fix this we move the assignments to the svc_fh later, after all possible error cases have been detected.
Title nfsd: fix refcount leak in nfsd_set_fh_dentry()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2025-11-24T13:04:20.888Z

Reserved: 2025-04-16T07:20:57.179Z

Link: CVE-2025-40212

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2025-11-24T13:16:02.813

Modified: 2025-11-24T13:16:02.813

Link: CVE-2025-40212

cve-icon Redhat

Severity : Important

Publid Date: 2025-11-24T00:00:00Z

Links: CVE-2025-40212 - Bugzilla

cve-icon OpenCVE Enrichment

No data.