CVE-2025-21965 sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl()

What is CVE-2025-21965?

CVE-2025-21965 is a high-severity vulnerability in Linux kernel, published on 1 Apr 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:

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.

Weakness: CWE-476

Which versions are affected by CVE-2025-21965?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2025-21965?

Apply the vendor's patch.

Is CVE-2025-21965 being exploited?

There is no known exploitation of CVE-2025-21965 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2025-21965, DEBIAN-CVE-2025-21965, GHSA-9gr8-3pvc-4w93, UBUNTU-CVE-2025-21965.