CVE-2025-40212
NoneCVSS
—
EPSS
0.4%
Published
Nov 24, 2025
CISA due date
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The record
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.
Affected packages
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| Linux | Kernel | 6.12.0 | 6.12.59 |
| openSUSE:Leap 16.0 | dtb-aarch64 | 0 | 6.12.0-160000.9.1 |
| openSUSE:Leap 16.0 | kernel-64kb | 0 | 6.12.0-160000.9.1 |
| openSUSE:Leap 16.0 | kernel-azure | 0 | 6.12.0-160000.9.1 |
| openSUSE:Leap 16.0 | kernel-default | 0 | 6.12.0-160000.9.1 |
| openSUSE:Leap 16.0 | kernel-default-base | 0 | 6.12.0-160000.9.1.160000.2.6 |
| openSUSE:Leap 16.0 | kernel-docs | 0 | 6.12.0-160000.9.1 |
| openSUSE:Leap 16.0 | kernel-kvmsmall | 0 | 6.12.0-160000.9.1 |
| openSUSE:Leap 16.0 | kernel-obs-build | 0 | 6.12.0-160000.9.1 |
| openSUSE:Leap 16.0 | kernel-obs-qa | 0 | 6.12.0-160000.9.1 |
| openSUSE:Leap 16.0 | kernel-rt | 0 | 6.12.0-160000.9.1 |
| openSUSE:Leap 16.0 | kernel-source | 0 | 6.12.0-160000.9.1 |
| openSUSE:Leap 16.0 | kernel-syms | 0 | 6.12.0-160000.9.1 |
| openSUSE:Leap 16.0 | kernel-zfcpdump | 0 | 6.12.0-160000.9.1 |
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