CVE-2025-21856 s390/ism: add release function for struct device
A missing release function in the s390 ISM driver allows use-after-free, potentially enabling local attackers to execute code or escalate privileges.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-21856?
CVE-2025-21856 is a high-severity use after free vulnerability in Linux kernel, published on 12 Mar 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Weakness: CWE-416
Which versions are affected by CVE-2025-21856?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21856?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2025-21856 being exploited?
There is no known exploitation of CVE-2025-21856 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-21856, DEBIAN-CVE-2025-21856, GHSA-m7rv-xwhq-qx85, UBUNTU-CVE-2025-21856.