# CVE-2025-21795

## Summary

- **CVE ID:** CVE-2025-21795
- **Severity:** HIGH
- **CVSS Score:** 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
- **CWE:** N/A
- **Published:** Feb 27, 2025
- **Last Modified:** Sep 8, 2026

## 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 — Linux (67ef9e5fd737eab2495f2586df7e9ea30caa1b77)
- Linux — Linux (26540b8940a2e21582afa61a6fb8af87310bac72)
- Linux — Linux (66af25799940b26efd41ea6e648f75c41a48a2c2)
- Linux — Linux (5.19)
- Linux — Linux (0)
- Linux — Linux (5.10.235)
- Linux — Linux (5.15.179)
- Linux — Linux (6.1.129)
- Linux — Linux (6.6.79)
- Linux — Linux (6.12.16)
- Linux — Linux (6.13.4)
- Linux — Linux (6.14)
- Linux — Linux (5.10.220)
- Linux — Linux (5.15.154)

## References

- [CNA](https://git.kernel.org/stable/c/abed68027ea3ab893ac85cc46a00e2e64a324239)
- [CNA](https://git.kernel.org/stable/c/efa8a261c575f816c7e79a87aeb3ef8a0bd6b221)
- [CNA](https://git.kernel.org/stable/c/38d345f612503b850c2973e5a879f88e441b34d7)
- [CNA](https://git.kernel.org/stable/c/23ad7797c74cd8f7f90617f1e59a8703e2b43908)
- [CNA](https://git.kernel.org/stable/c/cedfbb92cf97a6bff3d25633001d9c44442ee854)
- [CNA](https://git.kernel.org/stable/c/e88d2451cd42e025465d6b51fd716a47b0b3800d)
- [CNA](https://git.kernel.org/stable/c/036ac2778f7b28885814c6fbc07e156ad1624d03)
- [CVE](https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html)
- [CVE](https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html)
- [siemens-SADP](https://cert-portal.siemens.com/productcert/html/ssa-265688.html)
- [siemens-SADP](https://cert-portal.siemens.com/productcert/html/ssa-082556.html)
- [siemens-SADP](https://cert-portal.siemens.com/productcert/html/ssa-019113.html)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.63%
- **EPSS Percentile:** 48.6

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._