# CVE-2025-39871

## Summary

- **CVE ID:** CVE-2025-39871
- **Severity:** HIGH
- **CVSS Score:** 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** N/A
- **Published:** Sep 23, 2025
- **Last Modified:** Sep 8, 2026

## Description

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

dmaengine: idxd: Remove improper idxd_free

The call to idxd_free() introduces a duplicate put_device() leading to a
reference count underflow:
refcount_t: underflow; use-after-free.
WARNING: CPU: 15 PID: 4428 at lib/refcount.c:28 refcount_warn_saturate+0xbe/0x110
...
Call Trace:
 <TASK>
  idxd_remove+0xe4/0x120 [idxd]
  pci_device_remove+0x3f/0xb0
  device_release_driver_internal+0x197/0x200
  driver_detach+0x48/0x90
  bus_remove_driver+0x74/0xf0
  pci_unregister_driver+0x2e/0xb0
  idxd_exit_module+0x34/0x7a0 [idxd]
  __do_sys_delete_module.constprop.0+0x183/0x280
  do_syscall_64+0x54/0xd70
  entry_SYSCALL_64_after_hwframe+0x76/0x7e

The idxd_unregister_devices() which is invoked at the very beginning of
idxd_remove(), already takes care of the necessary put_device() through the
following call path:
idxd_unregister_devices() -> device_unregister() -> put_device()

In addition, when CONFIG_DEBUG_KOBJECT_RELEASE is enabled, put_device() may
trigger asynchronous cleanup via schedule_delayed_work(). If idxd_free() is
called immediately after, it can result in a use-after-free.

Remove the improper idxd_free() to avoid both the refcount underflow and
potential memory corruption during module unload.

## Affected Products

- Linux — Linux (68ac5a01f635b3791196fd1c39bc48497252c36f)
- Linux — Linux (d2d05fd0fc95c4defed6f7b87550e20e8baa1d97)
- Linux — Linux (21f9f5cd9a0c75084d4369ba0b8c4f695c41dea7)
- Linux — Linux (d5449ff1b04dfe9ed8e455769aa01e4c2ccf6805)
- Linux — Linux (2b7a961cea0e5b65afda911f76d14fec5c98d024)
- Linux — Linux (6.15)
- Linux — Linux (0)
- Linux — Linux (6.1.160)
- Linux — Linux (6.6.107)
- Linux — Linux (6.12.48)
- Linux — Linux (6.16.8)
- Linux — Linux (6.17)
- Linux — Linux (6.1.140)
- Linux — Linux (6.6.92)
- Linux — Linux (6.12.30)
- Linux — Linux (6.14.8)

## References

- [CNA](https://git.kernel.org/stable/c/24414bbcb37e1af95190af36c21ae51d497e1a9e)
- [CNA](https://git.kernel.org/stable/c/0e95ee7f532b21206fe3f1c4054002b0d21e3b9c)
- [CNA](https://git.kernel.org/stable/c/dd7a7e43269711d757fc260b0bbdf7138f75de11)
- [CNA](https://git.kernel.org/stable/c/da4fbc1488a4cec6748da685181ee4449a878dac)
- [CNA](https://git.kernel.org/stable/c/f41c538881eec4dcf5961a242097d447f848cda6)
- [siemens-SADP](https://cert-portal.siemens.com/productcert/html/ssa-019113.html)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.15%
- **EPSS Percentile:** 4.6

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