NULL Pointer Dereference Affecting perf6.18-debuginfo package, versions <1:6.18.36-69.134.amzn2023


Severity

Recommended
high

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.12% (3rd percentile)

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  • Snyk IDSNYK-AMZN2023-PERF618DEBUGINFO-18062134
  • published21 Jul 2026
  • disclosed1 Jul 2026

Introduced: 1 Jul 2026

NewCVE-2026-53328  (opens in a new tab)
CWE-476  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 perf6.18-debuginfo to version 1:6.18.36-69.134.amzn2023 or higher.
This issue was patched in ALAS2023-2026-1925.

NVD Description

Note: Versions mentioned in the description apply only to the upstream perf6.18-debuginfo package and not the perf6.18-debuginfo package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1