CVE-2025-40212
A critical flaw in the Linux kernel’s NFS server can be triggered by a specially crafted NFSv4 filehandle, leading to a use‑after‑free and potential denial of service. The bug was fixed in a kernel update that corrected reference counting in the nfsd_set_fh_dentry function.
An official fix is available, so this entry is kept for 30 days and then removed automatically.
Who is affected
Linux kernel NFS server (nfsd) components that handle NFSv4 filehandles.
Real-world impact
An attacker could send a malicious NFSv4 request to a vulnerable NFS server, causing the server to crash or become unresponsive, which could disrupt services for all clients relying on that server.
Why this severity
The CVSS score of 9.8 reflects that the vulnerability can be exploited remotely without authentication, and it compromises confidentiality, integrity, and availability of the NFS service.
What to do about it
- 01Upgrade the Linux kernel to a version that includes the nfsd_set_fh_dentry fix.
- 02Reboot the system to load the updated kernel.
NVD-referenced vendor advisory
Timeline
- Nov 24, 2025 · Nov 24, 2025PublishedDisclosed and added to the National Vulnerability Database.
- Jul 30, 2026 · 6h agoAdvisory updatedThe NVD record was last revised.
- Jul 30, 2026 · 3h agoOfficial fix availableA vendor patch or mitigation now exists — see the remediation steps above.