[CVE-2026-74345][IMPORTANT] RDMA/siw: Fix endpoint/socket association handling [ Upstream

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

CVE: CVE-2026-74345
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: RDMA/siw: Fix endpoint/socket association handling [ Upstream
Commit: b28d513393f81e2de00f82970487a9d001557e4e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b28d513393f81e2de00f82970487a9d001557e4e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74345
Analysis date: Sun, 16 Aug 2026 07:36:52 -0400
ActionableScore: 7
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A malformed MPA request to a reachable RDMA/siw listener can trigger a use-after-free in endpoint/socket disassociation during connection setup, causing at least a kernel crash and requiring manual review for possible heap UAF exploitation beyond DoS.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-74345 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74345

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: IMPORTANT
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-2026-74345	IMPORTANT	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-416;*CWE-672;*CWE-664;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '8.8';DESCR 'A use-after-free can occur in the RDMA/siw connection management path when siw_socket_disassoc() drops the last endpoint reference and the caller later accesses or clears the endpoint socket pointer. A remote peer can trigger this during connection establishment by sending a malformed MPA request to a reachable siw listener, causing the new endpoint to be closed and exposing the stale endpoint pointer. For the CVSS the PR:N is used because the attacker only needs network reachability to the RDMA/siw TCP service and does not need local code execution on the target. RDMA/siw endpoints are usually deployed on controlled data center or storage networks rather than the public Internet. Impact is at least denial of service via kernel crash. For the paranoid score, choose the highest still-defensible interpretation supported by the bug class and patch context, with preference for manual-review sensitivity over autoclosed false negatives. Because this is a kernel heap use-after-free, worst case impact may include confidentiality or integrity compromise and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6)	YES	UAF NETWORK KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* +2 Remote reachable / network-triggerable: a malformed MPA request can be sent by a remote peer to a reachable RDMA/siw listener during connection establishment.
* +2 Generic memory corruption: the commit explicitly reports KASAN slab-use-after-free in `siw_cm_work_handler`.
* +1 Real lifetime corruption: `siw_socket_disassoc()` can drop the last endpoint reference via `siw_cep_put()`, freeing the endpoint while callers still access it.
* +1 Reliable kernel crash / strong DoS: the reported KASAN UAF corresponds to a kernel crash class issue.
* -1 Corruption primitive constrained: the visible stale write is mainly `cep->sock = NULL`, with no demonstrated attacker-controlled payload or target selection.
* -1 Rare AND difficult-to-reach subsystem/configuration: RDMA/siw is typically deployed only in specific RDMA/storage/data-center environments, not as a default public service.

Paranoid additional signals:

* +1 Weak LPE concern: this is a kernel heap UAF with post-free access in a network-triggerable path, so limited C/I impact is technically worth manual review even though no reclaim or controlled replacement is shown.
* +1 Confidentiality impact plausible: only for paranoid triage, based on generic kernel heap UAF risk.
* +1 Integrity impact plausible: only for paranoid triage, based on stale write-after-free potential.

No strong LPE bonus is awarded because the patch does not show attacker-controlled reclaim, type confusion, callback control, arbitrary write, or refcount takeover.

Call-site confidence: high. The patch includes the relevant call sites that accessed `cep->sock` after `siw_socket_disassoc()`.

## 3. Reachability analysis

The bug is triggered during RDMA/siw connection management after processing a malformed MPA request. A remote peer can reach the vulnerable path if an SIW listener is active and reachable over the relevant network. No local code execution on the target is required for the network-triggered scenario, so the practical attacker privilege is network reachability rather than local privileges.

This is not a broad default Internet-facing path. SIW/RDMA endpoints are usually deployed in controlled storage or data-center networks, and the vulnerable service must be configured and listening. Containers and namespaces mainly affect who can create or expose SIW listeners, but they do not remove the remote-trigger aspect once such a listener exists.

## 4. Severity interpretation

Conservatively, this is at least a network-triggerable kernel UAF with reliable DoS, but with constrained visible post-free writes and limited deployment exposure. That makes the lower score borderline manual review rather than ordinary auto-close Moderate.

Paranoid interpretation is stronger because the bug is a confirmed kernel heap use-after-free in a remotely reachable connection setup path. Even without a demonstrated exploit primitive, this is the type of lifetime bug that can be underestimated during early triage and should be treated as a Strong Important candidate for manual analysis.

## 5. One-sentence report phrase

A malformed MPA request to a reachable RDMA/siw listener can trigger a use-after-free in endpoint/socket disassociation during connection setup, causing at least a kernel crash and requiring manual review for possible heap UAF exploitation beyond DoS.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: confirmed KASAN slab-use-after-free, network-triggerable connection setup path, and kernel heap lifetime corruption. Conservative impact is DoS, but paranoid triage should not auto-close this because limited privilege escalation or C/I impact cannot be ruled out from the patch alone.

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

Patch: RDMA/siw: Fix endpoint/socket association handling [ Upstream
Commit: b28d513393f81e2de00f82970487a9d001557e4e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b28d513393f81e2de00f82970487a9d001557e4e

Changed files:
  drivers/infiniband/sw/siw/siw_cm.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=b28d513393f81e2de00f82970487a9d001557e4e

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

The original Linux kernel CVE announcement for CVE-2026-74345 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74345

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:N/UI:N/S:U/C:N/I:N/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: 4
  Paranoid ActionableScore: 7

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

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).