[CVE-2026-93123][LOW] serial: qcom-geni: do not advance stale DMA completions [ Upstream

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

CVE: CVE-2026-93123
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: serial: qcom-geni: do not advance stale DMA completions [ Upstream
Commit: 231c84fe7ec40e4a06c398c0591d5b8e823d68e1
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=231c84fe7ec40e4a06c398c0591d5b8e823d68e1
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93123
Analysis date: Fri, 18 Sep 2026 06:23:37 -0400
ActionableScore: 2
ActionableScore lower bound: 1
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-2026-93123 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93123

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-2026-93123	LOW	https://www.kernelcve.org/list/?q=CVE-2026-93123 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:N/I:L/A:H';CWE-362;*CWE-664;CWE-667;CWE-703;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '5.3';DESCR 'A race in the qcom GENI serial DMA TX path can let a stale DMA completion advance the transmit fifo after uart_flush_buffer has reset it and after userspace has queued new bytes. This can discard newly written serial data because tx_remaining still describes the old DMA transfer while the fifo contents now belong to a later write. For the CVSS the PR:L is used because a local user or process needs access to the affected tty device and must be able to issue serial write and flush operations. The issue is not directly network reachable and does not provide a clear memory corruption primitive. Impact is mainly integrity loss in the serial transmit stream and possible denial of service for communication with an attached serial device.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	PRINTF-TTY SIMPLEFIX DMAorINTERRUPT HARDWARE LINUS  DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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

ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1. No floor or cap applied.
* Raw paranoid score: 2
* Paranoid score: 2. No floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Conservative signals:

* +1. Established kernel-maintained transmit queue integrity issue. A stale DMA TX completion can incorrectly advance the UART transmit fifo and discard newly queued bytes after uart_flush_buffer().
* 0. No Real UAF. The word stale refers to an old DMA completion state, not to post-lifetime use of a freed object.
* 0. No kernel memory corruption primitive is established. The patch does not show OOB access, UAF, double free, refcount misuse, arbitrary write, or controlled reclaim.
* 0. No reliable kernel crash is established. The demonstrated consequence is serial TX data loss, not host panic.
* 0. No confidentiality impact is established.
* 0. No authorization or security-boundary bypass is established.
* 0. No remote reachability is established. The issue is reached through local tty operations and hardware DMA completion timing.

Paranoid additional signal:

* +1. Device communication availability impact is plausible when discarded serial output disrupts communication with an attached device or console channel. This remains device or communication path DoS, not host-wide kernel DoS.

Non-awarded material signals:

* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Structured stale-object leverage not awarded because there is no post-free structured object consumption.
* Weak LPE not awarded because the bug only discards TX fifo bytes.
* Extra Availability beyond device communication disruption not awarded.
* C/I kernel impact not awarded merely because DMA and fifo state are involved.
* Concrete repeated release/refcount signal not awarded. There is no first release that can end object lifetime, no surviving dangling reference, and no second lifetime-mutating operation.
* FLOOR 5 not applied because there is no Real UAF and no repeated release/refcount mutation.

3. Reachability analysis

The likely trigger is a local userspace process with access to the affected qcom GENI serial tty device. The process needs to write data, invoke a transmit buffer flush, and hit the timing window where hardware DMA has completed but the DMA completion interrupt has not yet been handled. This is below host-admin in environments where the tty device is exposed to a user or service account, so HostAdminRequired is NO.

NamespaceScopedPrivilege is NO because this is not a namespace-scoped networking or container capability issue. There is no direct network trigger. Prior privileged setup may exist in practice if an administrator must expose the serial device to the attacker, but the vulnerable operation itself is ordinary tty I/O once the device is accessible.

The issue is hardware-specific to qcom GENI serial DMA TX. This is not treated as a rare-hardware penalty because the patch does not require physical attacker access or an exotic debug-only mode. The race requires a specific async ordering between DMA completion, flush, and a later write, but repeated local attempts may be possible if the tty is accessible.

4. Primitive and severity interpretation

The exact primitive is an invalid stale DMA completion state causing incorrect fifo advancement. It is not an active structured object UAF and not fixed stale storage after free. It is a logic race in TX queue accounting.

There is no concrete repeated release/refcount operation. The first operation does not free an object whose exact reference later receives a second put or release. The second operation is not a lifetime mutation. Therefore this is CLASS_C rather than CLASS_B.

The demonstrated consequence is loss of newly written serial TX bytes. The speculative consequence is disruption of a serial-attached device or serial console communication, but no kernel crash, privilege escalation, disclosure, or boundary bypass is supported by the patch.

ImportantCandidate is NO because the patch establishes data loss and possible device communication DoS, not memory corruption or unresolved lifetime leverage. AutoDowngradeAllowed is YES because no actionable kernel corruption or security-boundary primitive remains unresolved.

Likely operational severity is Low to ordinary Moderate depending on whether the affected serial channel carries critical control traffic.

5. One-sentence report phrase

A race in the qcom GENI serial DMA TX path can let a stale completion discard newly queued serial output after a flush, causing local serial data loss and possible communication DoS without evidence of kernel memory corruption or privilege escalation.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: this is a hardware-specific local serial data-loss race with no UAF, no corruption primitive, no host crash, no network trigger, and no security-boundary bypass.

7. Call-site confidence

Call-site confidence: high

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

Patch: serial: qcom-geni: do not advance stale DMA completions [ Upstream
Commit: 231c84fe7ec40e4a06c398c0591d5b8e823d68e1
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=231c84fe7ec40e4a06c398c0591d5b8e823d68e1

Changed files:
  drivers/tty/serial/qcom_geni_serial.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=231c84fe7ec40e4a06c398c0591d5b8e823d68e1

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

The original Linux kernel CVE announcement for CVE-2026-93123 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93123

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:L/UI:N/S:U/C:N/I:L/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H
  The Best / paranoid CVSS score: 5.3

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: 1
  Paranoid ActionableScore: 2

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).