[CVE-2026-98753][LOW] tty: tty_port: restore TTY_IO_ERROR on activation failure [ Upstream

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-98753
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: tty: tty_port: restore TTY_IO_ERROR on activation failure [ Upstream
Commit: 34d4f67472ef7a744970b772a8565ddc727788e2
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=34d4f67472ef7a744970b772a8565ddc727788e2
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98753
Analysis date: Sat, 24 Oct 2026 12:01:50 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A local TTY user can race failed port activation with hangup or ioctl processing and potentially crash the kernel by reaching a powered-down or deregistered driver path.

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

The original Linux kernel CVE announcement for CVE-2026-98753 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98753

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.

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

CVE-2026-98753	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98753 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE AEGIS_AS=1 LEGACY=LOW RESULT=DIFF (final Legacy and Aegis differ; FINAL: LOW, Aegis: 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:N/I:N/A:H';CWE-362;CWE-754;**CWE-476;BEST CVSS score: '4.7';DESCR 'A race between tty_port_open activation failure and a concurrent hangup or TTY ioctl can leave TTY_IO_ERROR cleared even though the port is not operational. A local process with access to the affected TTY can issue an ioctl during this narrow window, allowing a driver callback to access powered down hardware or invalid driver state and causing an unclocked MMIO fault, NULL pointer dereference, or kernel panic. For the CVSS the PR:L value is selected because reliable triggering requires local user context and access to the affected TTY device, while administrative privilege is not inherently required. This is a race and state handling flaw with a demonstrated kernel crash primitive, not a demonstrated UAF, OOB write, or information leak, so the supported impact is C:N I:N A:H and direct network reachability is absent. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 4.7 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE to LOW because the CVSS score, vector or bug class threshold rule was applied. final reconciliation stage LOW to LOW because the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH and V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED. The independent weaker Aegis shadow evaluated CVSS 4.7 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The models disagreed but the aggregation rules retained the production result. The final reported impact is LOW.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	PRINTF-TTY SIMPLEFIX RACE LINUS  DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED	-	-	checked

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

ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 1 (+1 local below-host-admin trigger, +1 plausible kernel crash, -1 narrow activation-failure race).
* Conservative score: 1; no floor or cap applied.
* Raw paranoid score: 1; no additional technically supported primitive.
* Paranoid score: 1.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Local unprivileged trigger: supplied evidence supports a local process with permission to access the affected TTY; host administration is not inherently required.
* +1 Reliable kernel crash / strong DoS: leaving `TTY_IO_ERROR` cleared can permit driver callbacks against a powered-down or deregistered port, causing NULL dereference, unclocked access, or panic.
* -1 Hard timing requirement: triggering requires an ioctl to land in the narrow interval between failed activation and restoration during concurrent hangup/open activity.
* No UAF, OOB write, repeated release, attacker-controlled overwrite, information disclosure, or authorization bypass is shown.
* No extra availability point: it would duplicate the same kernel crash.
* B5-R and B3-PENDING do not apply; there is no heap overwrite or shared-backing write.

3. Reachability analysis

The supported actor is a local process already permitted to open or issue ioctls on the affected TTY. No host UID 0, host capability, namespace capability, special hardware, or prior privileged configuration is established as necessary, although exposure depends on an affected driver and accessible device node. The race is repeatable in principle but explicitly narrow.

4. Primitive and severity reading

The primitive is invalid active-state consumption: failed activation leaves the I/O-error guard incorrectly cleared, allowing later ioctl processing to enter a driver for a nonoperational port. This is CLASS_C crash/DoS behavior, not memory corruption or a security-policy bypass. The patch supports panic-capable invalid access, but not useful leverage after excluding the crash. Therefore ImportantCandidate is NO and automatic Important-preserving treatment is unwarranted.

5. One-sentence report phrase

A local TTY user can race failed port activation with hangup or ioctl processing and potentially crash the kernel by reaching a powered-down or deregistered driver path.

6. Manual review advice

MANUAL CHECK RECOMMENDED

Confirm affected driver callbacks, device-node permissions, and practical race reliability.

7. Call-site confidence

Call-site confidence: medium

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

Patch: tty: tty_port: restore TTY_IO_ERROR on activation failure [ Upstream
Commit: 34d4f67472ef7a744970b772a8565ddc727788e2
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=34d4f67472ef7a744970b772a8565ddc727788e2

Changed files:
  drivers/tty/tty_port.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=34d4f67472ef7a744970b772a8565ddc727788e2

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

The original Linux kernel CVE announcement for CVE-2026-98753 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98753

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:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).