VulnerabilityPublished 1 Jul 2026Updated 23 Jul 2026

CVE-2026-53328: Linux kernel · sched_ext: Don't warn on NULL cgrp_moving_from in scx_cgroup_move_task()

Source GCVE Database

Not known to be exploited · CVSS 5.5 Medium.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

5.5Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 5% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 1 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-q89p-4x7p-f9v9

What to do

AI-suggested

A fix has been implemented in the Linux kernel to remove the warning on NULL cgrp_moving_from in scx_cgroup_move_task(). Since this is a resolved issue, users should update their Linux kernel to a version that includes this fix once available. Patch status is not explicitly confirmed in the provided data; check the vendor advisory or Linux kernel release notes for the official fixed version and apply updates accordingly.

Description

A vulnerability in the Linux kernel scheduler extension (sched_ext) caused a warning to trigger incorrectly when systemd's user manager modifies its own subtree_control with certain resource controllers enabled. This warning occurs due to a NULL pointer in the cgrp_moving_from field during a specific cgroup migration sequence involving CPU and memory controllers. The issue is a logic mismatch in the kernel's handling of cgroup identity versus css identity during task migration, leading to a benign but noisy warning rather than a functional failure.

Impact

The vulnerability does not impact confidentiality, integrity, or availability of the system. The CVSS vector indicates no impact on confidentiality or integrity but a high impact on availability due to the kernel WARN. However, this WARN is a warning message, not a crash or denial of service. There are no known exploits in the wild. The issue primarily causes noisy kernel warnings under specific conditions without functional disruption.

Summary

The Linux kernel sched_ext scheduler had a vulnerability where a WARN message was triggered in scx_cgroup_move_task() due to a NULL cgrp_moving_from pointer. This happens when systemd's user manager writes "+cpu +memory +pids" to its subtree_control while sched_ext is loaded. The root cause is a mismatch between how scx_cgroup_can_attach() and the migration logic identify cgroups and css, resulting in a legitimate css-only migration being mistaken for a missing preparation step. The fix involved removing the warning since the NULL cgrp_moving_from is expected in this scenario and does not indicate an error.

References

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