CVE Catalog

CVE-2026-53328

MediumCVSS 5.5
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.12%

2th percentile - higher than 2% of all known CVEs

Summary

A WARN warning was triggered in the Linux kernel's scx_cgroup_move_task() function during task migration by the sched_ext scheduler. The issue occurs when systemd modifies subtree_control and cgrp_moving_from is NULL, which is a legitimate CSS-based migration, not an error. The fix removes the warning while keeping ops.cgroup_prep_move() and ops.cgroup_move() paired.

Risk Assessment

The WARN warning may cause unnecessary logging and potential system disruption, especially during cgroup management by systemd with a loaded sched_ext scheduler. It poses no direct security threat but could mask real issues.

Recommendation

Update the Linux kernel to a version containing the fix (commit removing the WARN warning in kernel/sched/ext.c). Monitor system logs for warnings related to sched_ext and cgroups.

Other vulnerabilities in Linux kernel

See all
Original NVD description (English source)

In the Linux kernel, the following vulnerability has been resolved: sched_ext: Don't warn on NULL cgrp_moving_from in scx_cgroup_move_task() A WARN fires when systemd's user manager writes "+cpu +memory +pids" to its own subtree_control while a sched_ext scheduler is loaded: WARNING: at kernel/sched/ext.c:3227 scx_cgroup_move_task+0xa8/0xb0 scx_cgroup_move_task+0xa8/0xb0 sched_move_task+0x134/0x290 cpu_cgroup_attach+0x39/0x70 cgroup_migrate_execute+0x37d/0x450 cgroup_update_dfl_csses+0x1e3/0x270 cgroup_subtree_control_write+0x3e7/0x440 scx_cgroup_can_attach() arms cgrp_moving_from only when a task's cpu cgroup changes. It can still be NULL when scx_cgroup_move_task() runs, through this sequence: Step Result --------------------------------- ---------------------------------- 1. cpu enabled on cgroup G cpu css = A 2. cpu toggled off then on for G A killed, B created (same cgroup) 3. an exiting task keeps A alive migration skips it, A now stale 4. +memory migrates G stale A vs current B pulls cpu in 5. cpu attach runs for all tasks hits a live, cpu-unchanged task 6. scx_cgroup_move_task() on it cgrp_moving_from NULL -> WARN The mismatch is that scx_cgroup_can_attach() keys on cgroup identity while migration drives the move on css identity, so a NULL cgrp_moving_from here is a legitimate css-only migration, not a missing prep. The call is already gated on cgrp_moving_from, so just drop the warning. ops.cgroup_prep_move() and ops.cgroup_move() stay paired.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS