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CVE-2025-21657

5.5 · MEDIUM

In the Linux kernel, the following vulnerability has been resolved: sched_ext: Replace rq_lock() to raw_spin_rq_lock() in scx_ops_bypass() scx_ops_bypass() iterates all CPUs to re-enqueue all the…

Published Jan 21, 2025EPSS 0.18%

Overview

CVE-2025-21657 is a medium-severity vulnerability. It was published on January 21, 2025 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.5, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

In the Linux kernel, the following vulnerability has been resolved:

sched_ext: Replace rq_lock() to raw_spin_rq_lock() in scx_ops_bypass()

scx_ops_bypass() iterates all CPUs to re-enqueue all the scx tasks.

For each CPU, it acquires a lock using rq_lock() regardless of whether

a CPU is offline or the CPU is currently running a task in a higher

scheduler class (e.g., deadline). The rq_lock() is supposed to be used

for online CPUs, and the use of rq_lock() may trigger an unnecessary

warning in rq_pin_lock(). Therefore, replace rq_lock() to

raw_spin_rq_lock() in scx_ops_bypass().

Without this change, we observe the following warning:

===== START =====

[ 6.615205] rq->balance_callback && rq->balance_callback != &balance_push_callback

[ 6.615208] WARNING: CPU: 2 PID: 0 at kernel/sched/sched.h:1730 __schedule+0x1130/0x1c90

===== END =====

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/6268d5bc10354fc2ab8d44a0cd3b042d49a0417eRefgit.kernel.org/stable/c/d9e446dd63cee7161717a6a8414ba9c6435af764

How CyberStrike helps

Frequently asked questions

What is CVE-2025-21657?

CVE-2025-21657 is a medium-severity vulnerability. It was published on January 21, 2025 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2025-21657?

This vulnerability has a CVSS 3.1 base score of 5.5, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2025-21657?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2025-21657?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-21657 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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