CVE-2025-21965: linux kernel Null Dereference — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl() If a BPF scheduler provides an invalid CPU (outside the nr_cpu_ids range) as prev_cpu to scx_bpf_select_cpu_dfl() it can cause a kernel crash. To prevent this, validate prev_cpu in scx_bpf_select_cpu_dfl() and trigger an scx error if an invalid CPU is specified.

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CVSS v3.1 Score

5.5

MEDIUM

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

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor	Product	Versions
linux	linux_kernel	6.12 — 6.12.20
linux	linux_kernel	6.13 — 6.13.8
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/515680e76c536dd4aa8e2b5d674b0d441baddf5b https://git.kernel.org/stable/c/752b56bb76e2471197d25d6948d85753043b10da https://git.kernel.org/stable/c/9360dfe4cbd62ff1eb8217b815964931523b75b3

Frequently Asked Questions

What is CVE-2025-21965? +

In the Linux kernel, the following vulnerability has been resolved: sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl() If a BPF scheduler provides an invalid CPU (outside the nr_cpu_ids range) as prev_cpu to scx_bpf_select_cpu_dfl() it can cause a kernel crash. To prevent this, validate prev_cpu in scx_bpf_select_cpu_dfl() and trigger an scx error if an invalid CPU is specified. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2025-21965? +

CVE-2025-21965 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-21965? +

CVE-2025-21965 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-2025-21965? +

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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