# CVE-2025-39721

## Summary

- **CVE ID:** CVE-2025-39721
- **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:** Sep 5, 2025
- **Last Modified:** Sep 8, 2026

## Description

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

crypto: qat - flush misc workqueue during device shutdown

Repeated loading and unloading of a device specific QAT driver, for
example qat_4xxx, in a tight loop can lead to a crash due to a
use-after-free scenario. This occurs when a power management (PM)
interrupt triggers just before the device-specific driver (e.g.,
qat_4xxx.ko) is unloaded, while the core driver (intel_qat.ko) remains
loaded.

Since the driver uses a shared workqueue (`qat_misc_wq`) across all
devices and owned by intel_qat.ko, a deferred routine from the
device-specific driver may still be pending in the queue. If this
routine executes after the driver is unloaded, it can dereference freed
memory, resulting in a page fault and kernel crash like the following:

    BUG: unable to handle page fault for address: ffa000002e50a01c
    #PF: supervisor read access in kernel mode
    RIP: 0010:pm_bh_handler+0x1d2/0x250 [intel_qat]
    Call Trace:
      pm_bh_handler+0x1d2/0x250 [intel_qat]
      process_one_work+0x171/0x340
      worker_thread+0x277/0x3a0
      kthread+0xf0/0x120
      ret_from_fork+0x2d/0x50

To prevent this, flush the misc workqueue during device shutdown to
ensure that all pending work items are completed before the driver is
unloaded.

Note: This approach may slightly increase shutdown latency if the
workqueue contains jobs from other devices, but it ensures correctness
and stability.

## Affected Products

- Linux — Linux (e5745f34113b758b45d134dec04a7df94dc67131)
- Linux — Linux (5.18)
- Linux — Linux (0)
- Linux — Linux (6.1.162)
- Linux — Linux (6.6.103)
- Linux — Linux (6.12.44)
- Linux — Linux (6.16.4)
- Linux — Linux (6.17)

## References

- [CNA](https://git.kernel.org/stable/c/fa4c14a82747886d333d8baef0d26da86ba1ccf7)
- [CNA](https://git.kernel.org/stable/c/5858448a6c65d8ee3f8600570d3ce19febcb33be)
- [CNA](https://git.kernel.org/stable/c/fe546f5c50fc474daca6bee72caa7ab68a74c33d)
- [CNA](https://git.kernel.org/stable/c/e59a52e429e13df3feb34f4853a8e36d121ed937)
- [CNA](https://git.kernel.org/stable/c/3d4df408ba9bad2b205c7fb8afc1836a6a4ca88a)
- [siemens-SADP](https://cert-portal.siemens.com/productcert/html/ssa-019113.html)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.14%
- **EPSS Percentile:** 4.0

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