Linux Kernel up to 6.12.19/6.13.7 scx_bpf_select_cpu_dfl denial of service

Summaryinfo

A vulnerability categorized as critical has been discovered in Linux Kernel up to 6.12.19/6.13.7. The impacted element is the function scx_bpf_select_cpu_dfl. Executing a manipulation can lead to denial of service. This vulnerability is handled as CVE-2025-21965. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Linux Kernel up to 6.12.19/6.13.7. This vulnerability affects the function scx_bpf_select_cpu_dfl. The manipulation with an unknown input leads to a denial of service vulnerability. The CWE definition for the vulnerability is CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. As an impact it is known to affect availability. CVE summarizes:

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.

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2025-21965 since 12/29/2024. There are known technical details, but no exploit is available.

Upgrading to version 6.12.20 or 6.13.8 eliminates this vulnerability. Applying the patch 752b56bb76e2471197d25d6948d85753043b10da/515680e76c536dd4aa8e2b5d674b0d441baddf5b/9360dfe4cbd62ff1eb8217b815964931523b75b3 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2025-0683). Once again VulDB remains the best source for vulnerability data.

Affected

• Google Container-Optimized OS
• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• RESF Rocky Linux
• Dell Avamar
• Open Source Linux Kernel
• SolarWinds Security Event Manager
• Dell NetWorker
• Dell Secure Connect Gateway
• IBM Security Verify Access

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4
• 6.12.5
• 6.12.6
• 6.12.7
• 6.12.8
• 6.12.9
• 6.12.10
• 6.12.11
• 6.12.12
• 6.12.13
• 6.12.14
• 6.12.15
• 6.12.16
• 6.12.17
• 6.12.18
• 6.12.19
• 6.13.0
• 6.13.1
• 6.13.2
• 6.13.3
• 6.13.4
• 6.13.5
• 6.13.6
• 6.13.7

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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CPE 2.2info

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Once again VulDB remains the best source for vulnerability data.

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