[CVE-2026-90267][LOW] scsi: sd: Fix special_vec mempool leak when scsi_alloc_sgtables() fails [ Upstream

[CVE-2026-90267][LOW] scsi: sd: Fix special_vec mempool leak when scsi_alloc_sgtables() fails [ Upstream

[AL-KERNEL]

CVE: CVE-2026-90267
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: scsi: sd: Fix special_vec mempool leak when scsi_alloc_sgtables() fails [ Upstream
Commit: 5d7d1b8b525e5eff33a01d07dfcf7bdd3b6d790d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5d7d1b8b525e5eff33a01d07dfcf7bdd3b6d790d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90267
Analysis date: Fri, 18 Sep 2026 08:04:57 -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-2026-90267 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90267

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-2026-90267	LOW	https://www.kernelcve.org/list/?q=CVE-2026-90267 CHECK WITH IMPACT FROM ORIG NN LOW	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-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A mempool page leak can occur in the SCSI sd driver when a special payload page is allocated for UNMAP or WRITE SAME and scsi_alloc_sgtables later fails before normal command uninitialization is armed. This is a local resource leak rather than a use after free or overwrite primitive. Repeated failures under memory pressure could gradually consume sd page pool or large page pool resources and may lead to denial of service. For the CVSS the PR:L value is used in the paranoid score because some deployments may allow a local process to trigger discard or write same indirectly through filesystem behavior or delegated block device access, but reliable triggering normally also depends on failure conditions such as memory pressure. The issue is not network reachable. Impact is denial of service only, with no supported confidentiality or integrity impact.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	INIT LEAK HARDWARE MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH 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=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

* +1 conservative. Concrete persistent kernel resource leak. `sd_set_special_bvec()` allocates a special payload page, and if `scsi_alloc_sgtables()` fails before normal command uninitialization is armed, that page is leaked.
* +1 paranoid. Potential resource-exhaustion concern if the failing path can be repeated under memory pressure or repeated discard / WRITE SAME activity.
* +0 Real UAF. No use-after-free, stale dereference, double free, or repeated release/refcount mutation is established.
* +0 Reliable kernel crash. The patch establishes a leak, not an immediate panic or fault.
* +0 Confidentiality and integrity. No disclosure, overwrite, ownership violation, authorization bypass, or protected-object modification is shown.
* +0 Remote reachability. No network-triggered path is established.
* +0 Strong exploitation leverage. No controlled reclaim, arbitrary write, active stale object reuse, callback influence, or privilege escalation primitive is shown.
* No race penalty. This is an ordered error path, not a timing race.
* No host-admin penalty. Host-admin-equivalent triggering is not positively established for all possible paths, so no unsupported -2 is applied.
* Concrete repeated release/refcount check: first release can end lifetime: no. Exact same reference survives after first release: no. Second lifetime/refcount mutation: no. Dedicated +1 repeated-release signal: not awarded. Paranoid repeated-refcount leverage: not awarded. FLOOR 5: not applied.

3. Reachability analysis

The affected path is in the SCSI disk driver for UNMAP and WRITE SAME command setup. A practical trigger requires a request that reaches `sd_setup_unmap_cmnd()`, `sd_setup_write_same10_cmnd()`, or `sd_setup_write_same16_cmnd()`, followed by `scsi_alloc_sgtables()` failure after the special payload page was allocated.

Ordinary below-host-admin reachability is not fully established from the supplied patch. Some systems may allow a local process to indirectly generate discard operations through filesystem activity when discard is enabled, but reliable triggering also depends on allocation failure or memory pressure. Direct block-device control is often privileged, but the evidence does not prove that host-admin-equivalent privilege is always required.

Namespace-scoped privilege is not established. The bug is not network reachable. Prior setup may include having an SCSI sd device and discard or WRITE SAME capable paths, but no rare hardware-only requirement is proven.

Race repeatability is not relevant because this is not a race. Repetition depends on repeatedly hitting the same allocation-failure error path.

4. Primitive and severity interpretation

The exact primitive is a missing cleanup of a mempool page allocated for special SCSI payload handling. This is a persistent kernel resource leak.

It is not active structured UAF and not fixed stale storage UAF. It is not cleanup/destructor stale dereference. There is no concrete repeated release/refcount operation. The first lifetime operation does not free the page and leave a dangling reference for a later second release. Instead, the problem is the opposite: the release is missing on an early error path.

PrimitiveClass is CLASS_C because the demonstrated security-relevant behavior is DoS-style resource leakage without an independently useful corruption primitive.

The demonstrated consequence is gradual resource loss. The speculative consequence is denial of service through accumulated leaks under repeatable failure conditions. There is no supported leverage beyond resource exhaustion. ImportantCandidate is NO because no memory corruption, ownership violation, authorization bypass, or unresolved lifetime/refcount mutation is present. AutoDowngradeAllowed is YES because this is a local resource leak without evidence of memory corruption or privilege escalation.

Likely operational severity is Low to ordinary Moderate.

5. One-sentence report phrase

A SCSI sd special payload mempool page can be leaked when `scsi_alloc_sgtables()` fails after UNMAP or WRITE SAME setup, and repeated failures may cause local resource-exhaustion DoS without evidence of memory corruption or privilege escalation.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: the patch establishes a concrete resource leak only, with no UAF, repeated release/refcount mutation, arbitrary write, disclosure, authorization bypass, or network exposure.

7. Call-site confidence

Call-site confidence: high

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

Patch: scsi: sd: Fix special_vec mempool leak when scsi_alloc_sgtables() fails [ Upstream
Commit: 5d7d1b8b525e5eff33a01d07dfcf7bdd3b6d790d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5d7d1b8b525e5eff33a01d07dfcf7bdd3b6d790d

Changed files:
  drivers/scsi/sd.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=5d7d1b8b525e5eff33a01d07dfcf7bdd3b6d790d

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

The original Linux kernel CVE announcement for CVE-2026-90267 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90267

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:L
  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: 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).