* [CVE-2026-97480][LOW] tty: serial: 8250: protect against NULL uart->port.dev in register [ Upstream
@ 2026-09-24 21:34 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-24 21:34 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-97480
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: tty: serial: 8250: protect against NULL uart->port.dev in register [ Upstream
Commit: 5cbab666721d974bfe033a12045d808936deaefd
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5cbab666721d974bfe033a12045d808936deaefd
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97480
Analysis date: Thu, 24 Sep 2026 17:34:51 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97480 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97480
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: LOW
Manual review required: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-97480 LOW https://www.kernelcve.org/list/?q=CVE-2026-97480 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';**CWE-476;BEST CVSS score: '4.4';DESCR 'A NULL pointer dereference can occur in serial8250_register_8250_port when both the existing UART slot and the supplied UART port have no parent device. The code passes a NULL uart port dev pointer to has_acpi_companion which dereferences the device pointer while checking the ACPI companion. This can cause a kernel Oops or panic during legacy non OF non ACPI serial port registration. For the CVSS the PR:H because reaching this registration path typically requires administrative control over driver loading device registration or platform configuration. The issue is not network reachable. Impact is denial of service only. The patch context does not show a use after free out of bounds access information leak or write primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) YES PRINTF-TTY HARDWARE LINUS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate**::
No floor or cap was applied.
2. Signal breakdown
* +1 Reliable kernel crash or strong DoS. A NULL `uart->port.dev` is passed to `has_acpi_companion()`, which dereferences `dev->fwnode`. This can generate a kernel Oops and may panic systems configured to panic on Oops.
* No remote reachability awarded. The vulnerable operation is an internal serial-port registration path, not packet processing or a remotely exposed protocol handler.
* No local unprivileged trigger awarded. The supplied patch does not establish that an ordinary local user can cause a legacy no-device 8250 port registration.
* No host-admin penalty applied. Host-admin-equivalent privilege is plausible for driver or platform registration, but it is not positively established by the supplied call-path evidence.
* No memory-corruption signal awarded. This is a direct NULL dereference, not a UAF, double free, OOB access, refcount mutation, or write primitive.
* No confidentiality or integrity signal awarded. No disclosure, unauthorized modification, or security-boundary bypass is established.
* No special race penalty applied. The defect is an ordered invalid-state condition, not a timing race.
3. Reachability analysis
The vulnerable function is reached when a kernel driver or legacy platform-registration caller invokes `serial8250_register_8250_port()` with no parent device and the selected existing UART slot also has no device pointer. The supplied context identifies legitimate legacy non-OF and non-ACPI callers, but does not identify a userspace interface through which an ordinary unprivileged user can create such a registration.
Administrative driver loading, platform-device setup, boot-time configuration, or an in-kernel caller may be required in practical deployments, but the complete privilege boundary is not visible. Therefore `HostAdminRequired=UNKNOWN`, not `YES`. No namespace-specific capability checks or complete namespace-reachable trigger path are shown, so `NamespaceScopedPrivilege=UNKNOWN`.
No special hardware is proven necessary beyond the presence of a relevant legacy serial registration path. No remote input, firmware-controlled input, or attacker-controlled serial data path reaches the faulty check.
4. Primitive and severity interpretation
The exact primitive is a NULL-pointer dereference in `has_acpi_companion(uart->port.dev)` when `uart->port.dev` remains NULL after conditional initialization. This is an invalid-state crash primitive, classified as `CLASS_C`.
There is no freed object, stale post-lifetime reference, RCU lifetime mismatch, repeated release, refcount mutation, active-object reuse, controlled replacement, callback consumption, arbitrary write, or information-disclosure path. The demonstrated consequence is kernel Oops or possible panic, which is a denial of service. Privilege escalation and confidentiality or integrity impact are speculative and unsupported by this patch.
`ImportantCandidate=NO` because there is no meaningful unresolved corruption or boundary-bypass primitive beyond the crash. `AutoDowngradeAllowed=YES` because the issue is a constrained NULL dereference with no demonstrated attacker-controlled memory-corruption leverage.
5. One-sentence report phrase
A NULL pointer dereference in serial8250_register_8250_port can crash the kernel when a legacy serial port registration has no parent device, but no memory-corruption or privilege-escalation primitive is established.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch fixes a direct NULL dereference in a legacy registration path. The supplied evidence establishes only crash-level impact and does not show unprivileged reachability, remote reachability, memory corruption, or a security-boundary bypass.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: tty: serial: 8250: protect against NULL uart->port.dev in register [ Upstream
Commit: 5cbab666721d974bfe033a12045d808936deaefd
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5cbab666721d974bfe033a12045d808936deaefd
Changed files:
drivers/tty/serial/8250/8250_core.c:767
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=5cbab666721d974bfe033a12045d808936deaefd
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97480 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97480
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: Not available
The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 4.4
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: unknown
Paranoid ActionableScore: 1
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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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