CVE-2025-21657

CVE-2025-21657 is a medium-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 5.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

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 =====

Frequently asked questions

What is CVE-2025-21657?
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 =====
How severe is CVE-2025-21657?
CVE-2025-21657 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2025-21657 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (7th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-21657?
CVE-2025-21657 primarily affects Linux Linux Kernel. In total, 10 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-21657?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-21657 have an EU (EUVD) identifier?
Yes. CVE-2025-21657 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-2606.
When was CVE-2025-21657 published?
CVE-2025-21657 was published on 2025-01-21 and last updated on 2026-06-17.

References

Affected products (10)

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