CVE-2025-21795: NFSD: fix hang in nfsd4_shutdown_callback

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-02-27 · updated 2026-10-15

Description

In the Linux kernel, the following vulnerability has been resolved: NFSD: fix hang in nfsd4_shutdown_callback If nfs4_client is in courtesy state then there is no point to send the callback. This causes nfsd4_shutdown_callback to hang since cl_cb_inflight is not 0. This hang lasts about 15 minutes until TCP notifies NFSD that the connection was dropped. This patch modifies nfsd4_run_cb_work to skip the RPC call if nfs4_client is in courtesy state.

Affected products

Linux kernel: from 5.10.220 before 5.10.235; from 5.15.154 before 5.15.179; from 5.19 before 6.1.129; from 6.2 before 6.6.79; from 6.7 before 6.12.16; from 6.13 before 6.13.4 — fixed in 5.10.235, 5.15.179, 6.1.129, 6.12.16, 6.13.4, 6.6.79

How to fix

Upgrade to a fixed version: Linux kernel 5.10.235, 5.15.179, 6.1.129, 6.12.16. Check the vendor advisory for mitigations.

References

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