#VU103011 Use-after-free in Linux kernel - CVE-2025-21631

Vulnerability identifier: #VU103011

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-2025-21631

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 bfq_waker_bfqq() function in block/bfq-iosched.c. A local user can escalate privileges on the system.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Linux kernel: 5.15 - 5.15.176, 6.1 - 6.1.124, 6.6 - 6.6.71, 6.12 - 6.12.9

---

External links
https://git.kernel.org/stable/c/2550149fcdf2934155ff625d76ad4e3d4b25bbc6
https://git.kernel.org/stable/c/bc2aeb35ff167e0c6b0cedf0c96a5c41e6cba1ed
https://git.kernel.org/stable/c/be3eed59ac01f429ac10aaa46e26f653bcf581ab
https://git.kernel.org/stable/c/fcede1f0a043ccefe9bc6ad57f12718e42f63f1d
https://mirrors.edge.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.15.177
https://mirrors.edge.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.1.125
https://mirrors.edge.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.12.10
https://mirrors.edge.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.13
https://mirrors.edge.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.6.72

---

Q & A

Can this vulnerability be exploited remotely?

Is there known malware, which exploits this vulnerability?