[CVE-2026-98358][MODERATE REGULAR] IB/iser: reject a remote invalidation of an unregistered direction [ Upstream

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

CVE: CVE-2026-98358
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: IB/iser: reject a remote invalidation of an unregistered direction [ Upstream
Commit: 198e4db9add54a50cce60a5d80b8f0ee5456b65a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=198e4db9add54a50cce60a5d80b8f0ee5456b65a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98358
Analysis date: Thu, 08 Oct 2026 01:44:52 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-98358 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98358

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 REGULAR
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
======================================================================

CVE-2026-98358	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98358 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE RESULT=DIFF (legacy and Aegis reconciliation differ; DECISION: legacy MODERATE vs Aegis MODERATE_KPANIC)	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-476;*CWE-20;CWE-754;BEST CVSS score: '5.3';DESCR 'An iSER initiator NULL pointer dereference occurs when a remote target sends an RDMA remote invalidation for a direction that was marked active but was never registered. This can happen for an iSCSI write command whose data is sent entirely as immediate data. The invalidation path can pass a NULL RDMA descriptor to iser_inv_desc and crash the initiator kernel. For the CVSS the PR:N assessment reflects that no local access or privileges on the initiator are required. The attacker must control a connected iSER target or be able to tamper with RDMA traffic. The attack vector is adjacent network because iSER normally operates on an RDMA fabric or within a data center network and is not normally exposed to the public Internet. Impact is denial of service through an initiator kernel Oops or panic. No information disclosure integrity impact or privilege escalation primitive is demonstrated by the NULL dereference. ';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)	MAYBE	KASAN OOB NULLPTR NETWORK DMAorINTERRUPT KERNEL_PANIC_PLUS_UAF HARDWARE LINUS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	-	-	checked

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

ActionableScore=3
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 3
* Paranoid score: 3
* Final recommended bucket: **Borderline / manual review recommended**::

No floor or cap applies. Conservative and paranoid scores are identical because the patch establishes a NULL-pointer dereference and kernel crash path, but no lifetime violation, post-free use, write primitive, disclosure, or security-boundary bypass.

2. Signal breakdown

* +2 Remote reachable / directly network-triggerable. A connected malicious or compromised iSER target can send an RDMA remote invalidation in response to a valid immediate-data write request. The malformed response reaches `iser_check_remote_inv()` through RDMA completion handling.
* +1 Reliable kernel crash / strong DoS. The supplied KASAN trace demonstrates a NULL-pointer dereference in `iser_inv_desc()` through `desc->sig_protected`, in kernel completion processing.

Important non-awarded signals:

* +0 Real UAF. No object is freed, released, replaced, or accessed after lifetime end. `desc` is NULL because registration was intentionally skipped for immediate-data writes.
* +0 Controlled reclaim, arbitrary write, type confusion, refcount mutation, or callback control. None is established.
* +0 Confidentiality and integrity. The dereference is a NULL access and no read-back, disclosure, unauthorized modification, or security-sensitive state mutation is shown.
* +0 Privilege escalation. No LPE or authorization-bypass mechanism is established.
* +0 Concrete repeated release/refcount operation. No first release, surviving dangling reference, or second lifetime-mutating operation exists.
* +0 Structured stale-object leverage. This is not a stale active object. The failure is an immediate NULL descriptor dereference.
* +0 Additional Availability. The demonstrated Oops or panic is already counted as the reliable DoS signal.
* No negative score is applied. iSER and RDMA deployment may be specialized, but the supplied evidence does not prove a rare hardware-only condition or a host-admin-only attacker prerequisite.

3. Reachability analysis

The evaluated attacker is a remote iSER target, or an actor able to tamper with the RDMA traffic of an established iSER connection. The trigger requires an initiator to issue an iSCSI write whose payload is entirely immediate data, followed by a target response containing `IB_WR_SEND_WITH_INV` for the unregistered outbound direction.

The vulnerability is adjacent-network reachable rather than Internet-reachable. iSER operates over an RDMA fabric and normally requires a configured initiator-target relationship, compatible RDMA transport, and an established iSCSI session. These conditions limit practical exposure, but they do not make the crash primitive local-only.

HostAdminRequired is UNKNOWN. The supplied patch does not establish whether creating or controlling the target endpoint requires host-admin-equivalent access in the evaluated deployment. It also does not establish that a below-host-admin local user can configure the complete iSER initiator and target path.

NamespaceScopedPrivilege is UNKNOWN. No namespace capability checks or complete namespace-scoped trigger path are supplied. The RXE software RDMA trace demonstrates reproducibility but does not establish unprivileged namespace reachability.

No race is required. The trigger is an ordered protocol response after a relevant immediate-data write command.

4. Primitive and severity interpretation

The exact primitive is a protocol-state validation failure causing a NULL RDMA descriptor to be passed to `iser_inv_desc()`. The descriptor is absent by design because immediate-data writes do not require memory registration, while the direction flag remains set. The target can send an invalid remote invalidation that causes the initiator to dereference that NULL descriptor.

This is neither active structured-object UAF nor fixed stale storage. It is an invalid-state NULL-pointer dereference. The patch adds descriptor-presence checks and rejects the invalid remote invalidation by terminating the connection.

The demonstrated consequence is initiator kernel Oops or panic and denial of service. A possible deployment-level consequence is interruption of storage access through the affected iSER connection. No useful attacker-controlled primitive remains after excluding the crash. There is no post-free access, overwrite, controlled replacement, refcount mutation, data disclosure, integrity violation, or privilege escalation evidence.

PrimitiveClass is CLASS_C because the patch demonstrates crash-capable invalid-state handling without an independently useful memory-corruption or lifetime primitive. ImportantCandidate is NO because there is no unresolved Class B lifetime or corruption leverage. AutoDowngradeAllowed is YES because the demonstrated impact is constrained to DoS and no meaningful exploitation primitive remains unresolved.

Likely operational severity is an actionable remote-adjacent storage-fabric DoS that merits validation where iSER is deployed, but it is not an Important-class memory-corruption candidate from the supplied evidence.

5. One-sentence report phrase

A malicious iSER target can send an invalid RDMA remote invalidation for an unregistered immediate-data write direction, causing a NULL-pointer dereference and denial of service on the iSER initiator.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

The issue is remotely triggerable from a connected or compromised iSER target and can crash the initiator kernel, but the patch establishes only a NULL-pointer DoS primitive without memory corruption, UAF, disclosure, integrity impact, or privilege escalation.

7. Call-site confidence

Call-site confidence: medium

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

Patch: IB/iser: reject a remote invalidation of an unregistered direction [ Upstream
Commit: 198e4db9add54a50cce60a5d80b8f0ee5456b65a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=198e4db9add54a50cce60a5d80b8f0ee5456b65a

Changed files:
  drivers/infiniband/ulp/iser/iser_initiator.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=198e4db9add54a50cce60a5d80b8f0ee5456b65a

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

The original Linux kernel CVE announcement for CVE-2026-98358 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98358

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: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: unknown
  Paranoid ActionableScore: 3

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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

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).