[CVE-2026-80691][MODERATE 7.0] scsi: target: iblock: Fix wrong PR ops NULL check for PREEMPT/RELEASE [ Upstream

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

CVE: CVE-2026-80691
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: scsi: target: iblock: Fix wrong PR ops NULL check for PREEMPT/RELEASE [ Upstream
Commit: 3c60a8b4037dc35e365658fcbcb349a5d742ff49
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3c60a8b4037dc35e365658fcbcb349a5d742ff49
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80691
Analysis date: Fri, 28 Aug 2026 04:20:56 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A NULL function pointer dereference in the SCSI target iblock PR OUT path can allow a remote storage initiator with access to an exported iblock backed LUN to crash the kernel by sending PREEMPT, PREEMPT_AND_ABORT, or RELEASE commands when the matching block PR callback is unsupported.

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

The original Linux kernel CVE announcement for CVE-2026-80691 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80691

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: MODERATE 7.0
Manual review required: YES

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
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CVE-2026-80691	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-754;CWE-703;Other CVSS 'AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'A NULL function pointer dereference in the SCSI target iblock PR OUT path can occur because iblock_execute_pr_out checks ops pr_clear while later calling ops pr_preempt or ops pr_release. A remote storage initiator can trigger the path by sending PREEMPT, PREEMPT_AND_ABORT, or RELEASE persistent reservation commands to an exported iblock backed LUN when the underlying block device does not implement the matching callback. For the CVSS the PR:N is used for the paranoid case because a remote initiator may trigger the path with only access to an exported target endpoint, although many deployments restrict this with ACLs or authentication. The issue is network reachable when the target is exposed through iSCSI or another SCSI fabric. Impact is denial of service via kernel crash. No clear information disclosure or privilege escalation primitive is shown by the code change because the observed primitive is a NULL callback dereference.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)  SKIP CVE-2026-80691 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	INIT SIMPLEFIX IMPROVEONLY  KPANIC INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS	-	-	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: **4**
* Paranoid score: **5**
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* **Remote reachable / network-triggerable: +2**
  The affected code is in the SCSI target iblock backend and can be reached through exported storage fabrics such as iSCSI when an initiator can send SCSI Persistent Reservation OUT commands.

* **Reliable kernel crash / strong DoS: +1**
  The patch description explicitly says the wrong capability check can allow dereferencing a NULL function pointer.

* **Important filesystem/storage path: +1**
  The bug is in the kernel SCSI target storage path for iblock LUNs.

* **Rare AND difficult-to-reach subsystem/configuration: -1**
  Linux SCSI target with iblock PR support is not a default exposure on most systems and requires configured exported LUNs.

* **Availability impact realistic: +1**
  A NULL function pointer dereference in target context is a realistic host kernel crash when the vulnerable command path is reachable.

Conservative total: **4**

Paranoid adjustment:

* Remove the configuration rarity penalty in exposed storage-target environments: **+1 effective difference**
  If the system intentionally exposes an iblock-backed SCSI target to initiators, reachability is not rare inside that deployment.

Paranoid total: **5**

No extra points awarded for:

* **Privilege escalation plausible: +0**
  The patch supports a NULL callback dereference, not UAF, controlled overwrite, type confusion, or callback pointer control.

* **Generic memory corruption: +0**
  This is an invalid NULL function pointer call, not a demonstrated attacker-controlled memory corruption primitive.

* **Confidentiality / Integrity: +0**
  No supported info leak, unauthorized write, object confusion, or privilege boundary bypass is shown.

## 3. Reachability analysis

A remote storage initiator may trigger the vulnerable path by issuing PR OUT operations such as PREEMPT, PREEMPT_AND_ABORT, or RELEASE to an exported iblock-backed LUN when the underlying block device lacks the corresponding PR callback. In typical deployments this requires access to the configured SCSI target and LUN, often gated by iSCSI ACLs, CHAP, zoning, or trusted storage network placement. It is not generally Internet-facing by default.

Namespaces and containers usually do not matter for the remote trigger itself, because the relevant boundary is access to the storage target endpoint. Local administrative privileges are required to configure the vulnerable target, but not necessarily to trigger the crash once an initiator is authorized or the endpoint is exposed.

## 4. Severity interpretation

This behaves like an **Actionable Moderate** issue rather than ordinary Low or full Important. The realistic impact is a network-reachable kernel DoS in configured SCSI target deployments. The theoretical impact does not currently extend to privilege escalation because the primitive is a NULL function pointer dereference, not controllable function pointer corruption or memory reuse.

The issue should not be auto-closed because storage targets are commonly reachable from remote hosts inside datacenter or SAN networks, and a host kernel crash from a protocol command path is operationally significant.

## 5. One-sentence report phrase

A NULL function pointer dereference in the SCSI target iblock PR OUT path can allow a remote storage initiator with access to an exported iblock backed LUN to crash the kernel by sending PREEMPT, PREEMPT_AND_ABORT, or RELEASE commands when the matching block PR callback is unsupported.

## 6. Manual review recommendation

**MANUAL CHECK REQUIRED**

YES REQUIRES MANUAL CHECK

Reason: the issue is potentially network-triggerable through storage fabrics and causes a kernel crash, even though the demonstrated primitive is DoS-only and does not currently support confidentiality, integrity, or privilege escalation impact.

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

Patch: scsi: target: iblock: Fix wrong PR ops NULL check for PREEMPT/RELEASE [ Upstream
Commit: 3c60a8b4037dc35e365658fcbcb349a5d742ff49
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3c60a8b4037dc35e365658fcbcb349a5d742ff49

Changed files:
  drivers/target/target_core_iblock.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=3c60a8b4037dc35e365658fcbcb349a5d742ff49

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

The original Linux kernel CVE announcement for CVE-2026-80691 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80691

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:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 7.5

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: 4
  Paranoid ActionableScore: 5

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: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0

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).