[CVE-2026-90414][MODERATE 7.0] IB/isert: reject PDUs declaring more data than was received [ Upstream

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

CVE: CVE-2026-90414
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: IB/isert: reject PDUs declaring more data than was received [ Upstream
Commit: b4706722ed3ea72882b3c986a19b4a1ba66384c4
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b4706722ed3ea72882b3c986a19b4a1ba66384c4
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90414
Analysis date: Thu, 17 Sep 2026 13:58:07 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-90414 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90414

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-90414	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-90414 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H';CWE-125;CWE-126;*CWE-20;*CWE-200;Other CVSS 'AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H';BEST CVSS score: '8.8';DESCR 'An out of bounds read in the iSER target receive path can occur because isert_recv_done accepts the data segment length declared in the iSCSI BHS without validating it against wc byte_len, the number of bytes actually received into the fixed receive descriptor. A remote RDMA or iSER initiator that reaches full feature phase can declare a data segment larger than the bytes sent and cause handlers such as isert_handle_iscsi_dataout or isert_handle_scsi_cmd to read past the descriptor. In the immediate data path, the oversized buffer can also be handed to the backend as SCSI WRITE data, so heap bytes past the descriptor may be written to backing storage and could become an information disclosure if the initiator can later read the affected blocks. For the CVSS the PR:N is used in the paranoid score because some iSCSI target deployments may allow an initiator to complete login based only on network reachability and target ACL policy, while stricter deployments with CHAP or tight initiator ACLs are closer to PR:L. The issue is adjacent network reachable in typical RDMA storage fabrics rather than Internet exposed. Impact includes kernel crash or KASAN out of bounds reports and plausible confidentiality impact from kernel heap over read.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6)	YES	READ KASAN OOB NETWORK LINUS TEST KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	NO	NO	checked

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

ActionableScore=6
ActionableScoreLower=5
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 5
* Conservative score: 5. No floor or cap applied.
* Raw paranoid score: 6
* Paranoid score: 6. No floor or cap applied.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Positive conservative signals:

* +2 Remote or adjacent-network reachable. A remote RDMA/iSER initiator can send a malformed PDU after login/full feature phase to the iSER target.
* +1 Concrete memory-safety primitive. The attacker-controlled BHS dlength is used to read beyond the fixed-size receive descriptor when wc->byte_len is smaller than ISER_HEADERS_LEN + dlength.
* +1 Reliable crash or strong DoS. KASAN reports slab-out-of-bounds in sg_copy_buffer, and a non-KASAN kernel may fault or crash depending on adjacent memory and access size.
* +1 Important storage data path. In the immediate-data path, over-read bytes can be handed to the SCSI backend as WRITE data, making the bug more security-relevant than an internal-only over-read.

Additional paranoid signal:

* +1 Confidentiality plausible. The immediate-data path may write heap bytes past the receive descriptor into backing storage, and an initiator with later read access to the affected blocks could potentially observe those bytes. This is plausible but not fully demonstrated in the supplied evidence.

Non-awarded material signals:

* +0 RealUAF not awarded. No use-after-free or stale lifetime object is established.
* +0 Strong LPE or strong exploitation leverage not awarded. No controlled reclaim, arbitrary kernel read/write, callback control, credential manipulation, or demonstrated privilege escalation is shown.
* +0 Integrity plausible not separately awarded. The backend write sink is already counted as an important storage-path consequence, and attacker-controlled protected-data modification is not demonstrated.
* +0 Extra Availability not awarded. The KASAN/OOB crash path is already counted once.
* +0 Race/timing penalty not applied. This is a direct malformed-PDU length-validation bug, not a timing race.
* +0 Rare hardware penalty not applied. iSER/RDMA is specialized, but the bug was reproduced with soft-RoCE and no kernel-side test hooks.

3. Reachability analysis

The evaluated attacker is a remote RDMA/iSER initiator, not a local host user and not a host administrator. The trigger requires the target to expose iSER and for the initiator to reach full feature phase. Deployments with CHAP, ACLs, or isolated storage fabrics may require authorized initiator access, but host-admin-equivalent privilege on the target is not required to send the malformed PDU once the connection is allowed.

This is best treated as adjacent-network reachable rather than general Internet remote exposure. iSER targets are normally deployed in RDMA storage or data-center networks. Prior privileged setup exists in the sense that an administrator must configure the iSER target, but that is normal service exposure and not attacker privilege. No namespace-scoped capability is involved. No race is required.

4. Primitive and severity interpretation

The exact primitive is an attacker-controlled out-of-bounds read from a fixed iSER receive descriptor caused by trusting the declared iSCSI BHS data-segment length instead of validating it against wc->byte_len. This is not a UAF and not a controlled overwrite of kernel memory.

The primitive is stronger than crash-only behavior because one path can pass the oversized receive-buffer range to the backend as SCSI WRITE data. That creates a plausible kernel-heap disclosure path if those written blocks can be read back by the initiator. However, read-back was not demonstrated, and there is no evidence of arbitrary write, controlled reclaim, or privilege escalation. Therefore this is CLASS_B rather than CLASS_A.

ImportantCandidate=YES because the bug is network-reachable in a storage target data path and establishes a real kernel OOB read with a plausible disclosure sink. AutoDowngradeAllowed=NO because automatically closing it as ordinary Moderate would risk losing a meaningful unresolved memory-disclosure/storage-path primitive.

5. One-sentence report phrase

A remote RDMA or iSER initiator can declare more iSCSI data than was actually received, causing the iSER target to read beyond its fixed receive descriptor and potentially crash the kernel or expose heap bytes through backend WRITE data.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Network-reachable kernel memory-safety issue with a concrete OOB read and plausible heap-disclosure path through backing storage.

7. Call-site confidence

Call-site confidence: high

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

Patch: IB/isert: reject PDUs declaring more data than was received [ Upstream
Commit: b4706722ed3ea72882b3c986a19b4a1ba66384c4
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b4706722ed3ea72882b3c986a19b4a1ba66384c4

Changed files:
  drivers/infiniband/ulp/isert/ib_isert.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=b4706722ed3ea72882b3c986a19b4a1ba66384c4

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

The original Linux kernel CVE announcement for CVE-2026-90414 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90414

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:A/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H
  The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 8.8

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: 5
  Paranoid ActionableScore: 6

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).