#VU105653 Use-after-free in Linux kernel - CVE-2025-21856

Vulnerability identifier: #VU105653

Vulnerability risk: Low

CVSSv4.0: 5.9 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2025-21856

CWE-ID: CWE-416

Exploitation vector: Local

Exploit availability: No

Vulnerable software:
Linux kernel
Operating systems & Components / Operating system

Vendor: Linux Foundation

Description

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to a use-after-free error within the ism_dev_release(), ism_probe(), device_del() and ism_remove() functions in drivers/s390/net/ism_drv.c. A local user can escalate privileges on the system.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Linux kernel: All versions

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External links
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

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Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.