CVE-2026-53328
Status: AnalyzedMedium (5.5)—
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:
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:
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.
Read full descriptionShow less
The call is already gated on cgrp_moving_from, so just drop the warning. ops.cgroup_prep_move() and ops.cgroup_move() stay paired.
Technical details traces, logs and code from the original report
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 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
CVSS
- Version: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Base score: 5.5
Exploitation probability (EPSS)
- Probability of exploitation in the next 30 days: 0.13%
- Percentile among all scored CVEs: 2
- Score date: 10/4/2026
EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).
Affected technologies (1)
CWEs
- NVD-CWE-noinfo
References
Raw JSON (NVD)
Show
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Don't warn on NULL cgrp_moving_from in scx_cgroup_move_task()\n\nA WARN fires when systemd's user manager writes \"+cpu +memory +pids\" to\nits own subtree_control while a sched_ext scheduler is loaded:\n\n WARNING: at kernel/sched/ext.c:3227 scx_cgroup_move_task+0xa8/0xb0\n scx_cgroup_move_task+0xa8/0xb0\n sched_move_task+0x134/0x290\n cpu_cgroup_attach+0x39/0x70\n cgroup_migrate_execute+0x37d/0x450\n cgroup_update_dfl_csses+0x1e3/0x270\n cgroup_subtree_control_write+0x3e7/0x440\n\nscx_cgroup_can_attach() arms cgrp_moving_from only when a task's cpu\ncgroup changes. It can still be NULL when scx_cgroup_move_task() runs,\nthrough this sequence:\n\n Step Result\n --------------------------------- ----------------------------------\n 1. cpu enabled on cgroup G cpu css = A\n 2. cpu toggled off then on for G A killed, B created (same cgroup)\n 3. an exiting task keeps A alive migration skips it, A now stale\n 4. +memory migrates G stale A vs current B pulls cpu in\n 5. cpu attach runs for all tasks hits a live, cpu-unchanged task\n 6. scx_cgroup_move_task() on it cgrp_moving_from NULL -> WARN\n\nThe mismatch is that scx_cgroup_can_attach() keys on cgroup identity\nwhile migration drives the move on css identity, so a NULL cgrp_moving_from\nhere is a legitimate css-only migration, not a missing prep.\n\nThe call is already gated on cgrp_moving_from, so just drop the warning.\nops.cgroup_prep_move() and ops.cgroup_move() stay paired."
}
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"lastModified": "2026-07-23T20:52:41.010",
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