[CVE-2026-52941][LOW] net/smc: avoid NULL deref of conn->lnk in smc_msg_event tracepoint [ Upstream

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

CVE: CVE-2026-52941
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net/smc: avoid NULL deref of conn->lnk in smc_msg_event tracepoint [ Upstream
Commit: 68200112534bb2acd1d7117dc2d5c124868d866d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=68200112534bb2acd1d7117dc2d5c124868d866d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52941
Analysis date: Wed, 24 Jun 2026 05:29:05 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
An enabled SMC message tracepoint can NULL-dereference conn->lnk for SMC-D sockets during local sendmsg or recvmsg, causing a kernel crash, but exploitation is gated by tracing being enabled and does not show memory corruption or privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-52941 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52941

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.

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

CVE-2026-52941	LOW	CHECK	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-476;CWE-754;CWE-703;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'The smc_msg_event tracepoint can dereference smc conn lnk unconditionally when logging the device name, but conn lnk is NULL for SMC-D sockets. If the tracepoint is enabled, an SMC-D sendmsg or recvmsg path can reach strlen on a NULL derived address and crash the kernel. For the CVSS the PR:L is used in the paranoid score because the socket operation that triggers the fault can be performed by a local unprivileged user after tracing is already enabled by the system or administrator. The issue is not network reachable as a direct remote packet trigger and requires local code execution plus the SMC-D path and enabled tracepoint condition. Impact is denial of service only via kernel crash, with no supported evidence of confidentiality impact, integrity impact, UAF, OOB access, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)  SKIP CVE-2026-52941  SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	KASAN OOB NULLPTR TRACE KERNEL_PANIC_PLUS_UAF HARDWARE LINUS 	-	-	checked

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

ActionableScore=2
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Conservative scoring:

* Reliable kernel crash / strong DoS: +1
  With the tracepoint enabled, the SMC-D sendmsg or recvmsg path can reliably dereference NULL and crash.
* Requires admin/root/CAP_SYS_ADMIN in typical deployments: -2
  Enabling the relevant tracing path normally requires root or tracing privileges.
* Rare AND difficult-to-reach subsystem/configuration: -1
  The vulnerable condition requires SMC-D plus the specific tracepoint being enabled.
* Availability impact realistic: +1
  The resulting impact is a kernel crash, but this overlaps with the strong DoS signal. Counted only in the paranoid view, not conservative.

Paranoid scoring:

* Local unprivileged trigger: +1
  Once the tracepoint is enabled, socket(AF_SMC, ...) and SMC-D sendmsg or recvmsg can be triggered by an unprivileged local user.
* Reliable kernel crash / strong DoS: +1
  The crash path is direct and confirmed by the NULL-derived strlen fault.
* Rare AND difficult-to-reach subsystem/configuration: -1
  SMC-D availability and enabled tracepoint are non-default practical constraints.
* Availability impact realistic: +1
  In the enabled-tracepoint scenario, the crash is host-wide and easy to trigger.

Not applied:

* Remote reachable / network-triggerable: +0
  This is not a direct packet-triggered remote path.
* Generic memory corruption: +0
  This is a NULL pointer dereference, not UAF, OOB write, double-free, or type confusion.
* Privilege escalation plausible: +0
  No reclaim, overwrite, object confusion, or credential/security-boundary primitive is supported.
* Confidentiality / Integrity impact: +0
  No information disclosure or write primitive is shown.

## 3. Reachability analysis

The crash requires the smc_msg_event tracepoint to be enabled, which normally requires root or tracing privileges. After that precondition is satisfied, the actual trigger can be local and unprivileged because AF_SMC socket creation has no capability check. SMC-D must also be available, such as on s390 or on x86 with the loopback ISM device loaded. Containers or namespaces do not clearly make tracepoint enabling unprivileged in a typical host setup, so the conservative view treats this as admin-gated. The paranoid view treats an already-enabled tracepoint as an environmental precondition and scores the local unprivileged trigger.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like DoS issue rather than an Important-class vulnerability. The bug is a direct NULL dereference in tracepoint string collection. There is no evidence of UAF, object lifetime corruption, OOB access, attacker-controlled overwrite, or privilege escalation. The practical risk is mainly a local crash when a privileged administrator or tracing setup has already enabled the affected tracepoint.

## 5. One-sentence report phrase

An enabled SMC message tracepoint can NULL-dereference conn->lnk for SMC-D sockets during local sendmsg or recvmsg, causing a kernel crash, but exploitation is gated by tracing being enabled and does not show memory corruption or privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: this is a constrained NULL dereference DoS with an admin-gated tracepoint precondition and no supported memory corruption, information disclosure, or privilege-escalation primitive.

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

Patch: net/smc: avoid NULL deref of conn->lnk in smc_msg_event tracepoint [ Upstream
Commit: 68200112534bb2acd1d7117dc2d5c124868d866d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=68200112534bb2acd1d7117dc2d5c124868d866d

Changed files:
  net/smc/smc_tracepoint.h
  net/smc/smc_rx.c
  net/smc/af_smc.c
  net/socket.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=68200112534bb2acd1d7117dc2d5c124868d866d

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

The original Linux kernel CVE announcement for CVE-2026-52941 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52941

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:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  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: 0
  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).