[CVE-2026-53384][MODERATE 7.0] serial: 8250_dw: unregister 8250 port if clk_notifier_register() fails [ Upstream

[CVE-2026-53384][MODERATE 7.0] serial: 8250_dw: unregister 8250 port if clk_notifier_register() fails [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53384
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: serial: 8250_dw: unregister 8250 port if clk_notifier_register() fails [ Upstream
Commit: ccdf4510a3873b14e5e348cdb038717996f09fda
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ccdf4510a3873b14e5e348cdb038717996f09fda
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53384
Analysis date: Sun, 19 Jul 2026 09:13:04 -0400
ActionableScore: 7
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A failed clk_notifier_register() path in 8250_dw can leave an 8250 port registered after devm driver data is freed, creating a local stale callback UAF hazard with likely DoS impact and possible privilege escalation concern requiring manual review.

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ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-53384 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53384

The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.

The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.

Published priority for this report: MODERATE 7.0
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-53384	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;*CWE-672;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A use after free hazard exists in the 8250_dw serial driver because dw8250_probe can return after clk_notifier_register fails while the 8250 port remains registered. The registered port can still reference devm freed driver data through private_data and serial_in or serial_out callbacks, so later access to the stale port slot may dereference freed memory. For the CVSS the PR:L is used for the paranoid score because a local user or service with access to the affected tty or serial device may be able to trigger the stale callback path after the failed probe state exists. The issue is not network reachable and requires local device access plus a specific probe failure condition, so AC:H is retained. Impact is at least local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to kernel UAF behavior.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6)	YES	INIT PRINTF-TTY RACE ERRORPATH UAF HARDWARE BOOT KPANIC 	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=7
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

* Memory corruption, strong corruption primitive: +2. The port remains registered after probe failure while devm allocated driver data is freed, creating a real UAF hazard.
* Real lifetime corruption: +1. The stale 8250 port retains references through private_data and serial_in or serial_out callbacks after the backing object lifetime ended.
* Reliable kernel crash / strong DoS: +1. Later access to the stale port can dereference freed memory and plausibly crash the kernel.
* Privileged kernel/device-management memory corruption path: +1. The bug is in a serial driver probe/error path and leaves a globally registered kernel device object inconsistent.
* Local unprivileged trigger, paranoid only: +1. If the failed probe state already exists and the stale tty or serial port node is accessible, a local user or service may be able to trigger the stale callback path.
* Privilege escalation plausible, paranoid only: +2. This is not a proven LPE, but a kernel UAF through stale callbacks is a plausible manual-review candidate.
* Hard or special failure condition: -1. Reliable exploitation depends on clk_notifier_register() failing after serial8250_register_8250_port() succeeds.
* No demonstrated attacker-controlled reclaim or overwrite target: -1 conservative. The patch does not show controlled object replacement, arbitrary write, or a demonstrated exploit primitive.

## 3. Reachability analysis

The initial bad state is created during dw8250_probe() when clock notifier registration fails after the 8250 port was registered. In typical deployments, forcing probe/rebind or influencing the clock notifier path is likely privileged or hardware/platform dependent. After the bad state exists, the stale registered port may be reachable through normal serial/tty access paths, depending on device permissions and udev policy. This is not network reachable. Containers and namespaces usually do not expose this hardware control path directly, but reduced-privilege service accounts with serial device access could be relevant for the paranoid interpretation.

## 4. Severity interpretation

This is more than an ordinary cleanup bug because the commit explicitly describes freed devm driver data still reachable from a registered 8250 port. The realistic impact is most likely local DoS through a kernel crash under a special probe failure condition. The theoretical worst case is more serious because stale callback paths over freed kernel driver data can sometimes become exploitable if object reuse is controllable, but that is not demonstrated by the patch.

## 5. One-sentence report phrase

A failed clk_notifier_register() path in 8250_dw can leave an 8250 port registered after devm driver data is freed, creating a local stale callback UAF hazard with likely DoS impact and possible privilege escalation concern requiring manual review.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED.

Reason: the bug is an explicit kernel UAF lifetime issue involving stale private_data and serial callback paths, even though practical exploitation requires a special probe failure condition and no controlled reclaim primitive is shown.

======================================================================
UPSTREAM PATCH SUMMARY
======================================================================

Patch: serial: 8250_dw: unregister 8250 port if clk_notifier_register() fails [ Upstream
Commit: ccdf4510a3873b14e5e348cdb038717996f09fda
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ccdf4510a3873b14e5e348cdb038717996f09fda

Changed files:
  drivers/tty/serial/8250/8250_dw.c

Diff excerpt:

Not included in this email. See the upstream URL for the full patch.

Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ccdf4510a3873b14e5e348cdb038717996f09fda

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-53384 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53384

The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.

The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.

The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.

Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:

  Conservative CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7

The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.

CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.

A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.

  Conservative ActionableScore: 4
  Paranoid ActionableScore: 7

The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.

For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:

  ActionableScore below 5   -> MODERATE REGULAR
  ActionableScore 5 or more -> MODERATE 7.0

The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.

There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).

KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.

AL-KERNEL base severity for this report: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0

These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).

Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).