[CVE-2026-93781][LOW] scsi: core: Do not block on tag allocation in scsi_eh_lock_door() [ Upstream

[CVE-2026-93781][LOW] scsi: core: Do not block on tag allocation in scsi_eh_lock_door() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-93781
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: scsi: core: Do not block on tag allocation in scsi_eh_lock_door() [ Upstream
Commit: 261c80a6b23e34ba98bcf3f75317e35ecf0a08f0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=261c80a6b23e34ba98bcf3f75317e35ecf0a08f0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93781
Analysis date: Thu, 24 Sep 2026 20:01:31 -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-2026-93781 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93781

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-2026-93781	LOW	https://www.kernelcve.org/list/?q=CVE-2026-93781 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';*CWE-833;CWE-667;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.3';DESCR 'A SCSI error recovery deadlock can occur because scsi_eh_lock_door waits for a scheduler tag while the host remains in SHOST_RECOVERY. The required tag can be held by commands that were requeued during error handling, but those commands cannot be dispatched or completed until the same error handler exits recovery and restarts the queues. This creates a circular wait and can permanently block I O, especially on devices with a single driver tag such as some USB storage devices. For the CVSS the paranoid PR:N applies only when an attacker can control an unauthenticated adjacent or network attached SCSI target that can induce device errors. The normal local case is PR:L because a local process must generate I O activity and the trigger also requires a device error and tag exhaustion. The issue is not a direct Internet reachable vulnerability. Impact is denial of service only through stalled storage I O. No memory corruption or privilege escalation primitive is indicated.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	LOCK DEADLOCK ERRORPATH HARDWARE  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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

ActionableScore=2
ActionableScoreLower=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: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate**::

The conservative score counts the established persistent I O deadlock. The paranoid score additionally considers a deployment with an attacker controlled adjacent or network attached SCSI target that can induce SCSI error recovery. No floor or cap was applied.

2. Signal breakdown

* +1 Reliable denial of service. The patch establishes a circular wait in SCSI error recovery. The error handler waits for a scheduler tag held by requeued commands, while those commands cannot run until that same error handler completes recovery and restarts queues. On a device with one driver tag, the deadlock is described as guaranteed and pending I O cannot be submitted.
* +1 Paranoid only. Firmware mediated external influence. A hostile directly attached or network attached SCSI target could plausibly induce error recovery behavior. This is not direct network reachability and is not established as available in every affected deployment.

Important non awarded signals:

* No UAF, stale post lifetime use, double release, refcount mutation, OOB access, arbitrary write, or memory corruption is established.
* No confidentiality or integrity impact is established.
* No local unprivileged trigger point was awarded. A local process may generate I O, but the supplied evidence does not establish that it can reliably induce the required SCSI device error and error recovery sequence.
* No direct remote reachability point was awarded. The affected operation is reached through SCSI error recovery, not directly through ordinary network packet processing.
* No hard race penalty was applied. The defect is an ordered circular dependency, not a timing race.
* No host administrator penalty was applied. The supplied patch does not establish that complete triggering requires host administrator privilege.
* No niche subsystem penalty was applied. SCSI is broadly deployed, and the patch explicitly identifies USB storage as an affected example. However, broad exposure was not awarded because the specific error recovery and tag exhaustion condition is not shown to be routinely exercised.

3. Reachability analysis

The direct trigger requires a SCSI device to enter error recovery while scheduler tags are exhausted by requeued commands. A local process can contribute workload that consumes tags, but the supplied patch does not prove that an ordinary user can independently force the relevant device error and recovery state.

A malicious USB or other directly attached storage device may be able to influence error behavior, but this is device mediated input rather than direct remote reachability. A hostile iSCSI or other network attached SCSI target is a plausible paranoid model if the attacker already controls or can access the storage endpoint. The patch does not establish that such a target is unauthenticated, Internet exposed, or reachable by an arbitrary remote attacker.

No relevant capability check or complete namespace scoped trigger chain is shown. NamespaceScopedPrivilege is therefore UNKNOWN. HostAdminRequired is also UNKNOWN because the evidence does not resolve whether device attachment, target configuration, or error injection requires host administrative control in the evaluated deployment.

4. Primitive and severity interpretation

The exact primitive is a SCSI recovery deadlock caused by blocking scheduler tag allocation during SHOST_RECOVERY. Requeued commands retain tags but cannot be dispatched until recovery exits. Recovery cannot exit because scsi_eh_lock_door waits for one of those tags.

This is neither an active structured object lifetime violation nor fixed stale storage. No object is freed, reused, dereferenced after lifetime end, or modified through a dangling reference. There is no repeated release or refcount mutation.

The demonstrated consequence is persistent storage I O unavailability for the affected device or host queue path. The patch describes a guaranteed deadlock for single driver tag devices. A host wide kernel crash, information disclosure, integrity violation, privilege escalation, controlled corruption, or security boundary bypass is not supported by the patch.

PrimitiveClass is CLASS_C because the defect is a concrete availability failure without a useful corruption primitive. ImportantCandidate is NO and AutoDowngradeAllowed is YES because no unresolved memory corruption, lifetime, authorization, ownership, or cross boundary primitive remains.

5. One-sentence report phrase

A circular wait in SCSI error recovery can permanently block storage I O when scsi_eh_lock_door waits for a scheduler tag held by requeued commands that cannot run until recovery completes.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The established impact is a deadlock based denial of service only, with no memory corruption or privilege escalation primitive.

7. Call-site confidence

Call-site confidence: high

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

Patch: scsi: core: Do not block on tag allocation in scsi_eh_lock_door() [ Upstream
Commit: 261c80a6b23e34ba98bcf3f75317e35ecf0a08f0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=261c80a6b23e34ba98bcf3f75317e35ecf0a08f0

Changed files:
  drivers/scsi/scsi_error.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=261c80a6b23e34ba98bcf3f75317e35ecf0a08f0

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

The original Linux kernel CVE announcement for CVE-2026-93781 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93781

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:N/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/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).