CVE-2025-21856: linux kernel Use-After-Free — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: s390/ism: add release function for struct device According to device_release() in /drivers/base/core.c, a device without a release function is a broken device and must be fixed. The current code directly frees the device after calling device_add() without waiting for other kernel parts to release their references. Thus, a reference could still be held to a struct device, e.g., by sysfs, leading to potential use-after-free issues if a proper release function is not set.

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CVSS v3.1 Score

7.8

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness Type (CWE)

CWE-416 Use After Free

Affected Products

Vendor	Product	Versions
linux	linux_kernel	6.3 — 6.6.80
linux	linux_kernel	6.7 — 6.12.17
linux	linux_kernel	6.13 — 6.13.5
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/0505ff2936f166405d81d0d454a81d9c14124344 https://git.kernel.org/stable/c/915e34d5ad35a6a9e56113f852ade4a730fb88f0 https://git.kernel.org/stable/c/940d15254d2216b585558bcf36312da50074e711 https://git.kernel.org/stable/c/e26e8ac27351f457091459a0a355bacd06d5bb2b

Frequently Asked Questions

What is CVE-2025-21856? +

In the Linux kernel, the following vulnerability has been resolved: s390/ism: add release function for struct device According to device_release() in /drivers/base/core.c, a device without a release function is a broken device and must be fixed. The current code directly frees the device after calling device_add() without waiting for other kernel parts to release their references. Thus, a reference could still be held to a struct device, e.g., by sysfs, leading to potential use-after-free issues if a proper release function is not set. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2025-21856? +

CVE-2025-21856 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-21856? +

CVE-2025-21856 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-21856? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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