# CVE-2025-39925

## Summary

- **CVE ID:** CVE-2025-39925
- **Severity:** MEDIUM
- **CVSS Score:** 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
- **CWE:** N/A
- **Published:** Oct 1, 2025
- **Last Modified:** Sep 2, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:

can: j1939: implement NETDEV_UNREGISTER notification handler

syzbot is reporting

  unregister_netdevice: waiting for vcan0 to become free. Usage count = 2

problem, for j1939 protocol did not have NETDEV_UNREGISTER notification
handler for undoing changes made by j1939_sk_bind().

Commit 25fe97cb7620 ("can: j1939: move j1939_priv_put() into sk_destruct
callback") expects that a call to j1939_priv_put() can be unconditionally
delayed until j1939_sk_sock_destruct() is called. But we need to call
j1939_priv_put() against an extra ref held by j1939_sk_bind() call
(as a part of undoing changes made by j1939_sk_bind()) as soon as
NETDEV_UNREGISTER notification fires (i.e. before j1939_sk_sock_destruct()
is called via j1939_sk_release()). Otherwise, the extra ref on "struct
j1939_priv" held by j1939_sk_bind() call prevents "struct net_device" from
dropping the usage count to 1; making it impossible for
unregister_netdevice() to continue.

[mkl: remove space in front of label]

## Affected Products

- Linux — Linux (9d71dd0c70099914fcd063135da3c580865e924c)
- Linux — Linux (5.4)
- Linux — Linux (0)
- Linux — Linux (6.16.8)
- Linux — Linux (6.17)
- Linux — Linux (5.15.220)
- Linux — Linux (6.1.187)
- Linux — Linux (6.6.156)
- Linux — Linux (6.12.108)

## References

- [CNA](https://git.kernel.org/stable/c/da9e8f429139928570407e8f90559b5d46c20262)
- [CNA](https://git.kernel.org/stable/c/7fcbe5b2c6a4b5407bf2241fdb71e0a390f6ab9a)
- [CNA](https://git.kernel.org/stable/c/479d8a2aedcc1db16f14c1a8a9c74b5bdf18b9ac)
- [CNA](https://git.kernel.org/stable/c/2c88069fac2c792e228e6a4ae71c9b9b5b9a87a6)
- [CNA](https://git.kernel.org/stable/c/76957b618ce729c3bd1e782fbc9d9991af653925)
- [CNA](https://git.kernel.org/stable/c/4e154cb5e7681c2910e2dfa09f05e3469e333745)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.15%
- **EPSS Percentile:** 4.3

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-17._