Answer in brief
CVE-2025-40212 records a Critical severity (CVSS 9.8) vulnerability in nfsd: fix refcount leak in nfsd_set_fh_dentry(). The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=ef7f6c4904d03ccd7478e1ac20ed75f79c4ac444 <b6bc86ce3944b10b9fc181fc00c1a520a20ed965 || >=ef7f6c4904d03ccd7478e1ac20ed75f79c4ac444 <c83d7365cec5eb5ebeeee2a72e29b4ca58a7e4c2 || >=ef7f6c4904d03ccd7478e1ac20ed75f79c4ac444 <8a7348a9ed70bda1c1f51d3f1815bcbdf9f3b38c | b6bc86ce3944b10b9fc181fc00c1a520a20ed965, c83d7365cec5eb5ebeeee2a72e29b4ca58a7e4c2, 8a7348a9ed70bda1c1f51d3f1815bcbdf9f3b38c |
| Linux/Linuxgeneric | 6.12 | Not reported |
Published upstream
Nov 24, 2025
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 18, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
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.
Quoted source text, attributed separately from HOL analysis.