[CVE-2026-64279][MODERATE REGULAR] i2c: core: fix adapter deregistration race

[CVE-2026-64279][MODERATE REGULAR] i2c: core: fix adapter deregistration race

[AL-KERNEL]

CVE: CVE-2026-64279
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: i2c: core: fix adapter deregistration race
Commit: d39282f552dd6c35b9b84b4af78f1198c24f3373
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d39282f552dd6c35b9b84b4af78f1198c24f3373
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64279
Analysis date: Sat, 25 Jul 2026 12:41:37 -0400
ActionableScore: 4
ActionableScore lower bound: 2
Actionable bucket: Borderline manual review recommended / Actionable Moderate candidate
Manual review required: YES

Summary:
A race in i2c adapter deregistration can leave an adapter reachable by ID while teardown frees associated resources, allowing a local race to trigger stale resource access and potentially crash the kernel.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64279 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64279

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
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CVE-2026-64279	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-362;*CWE-416;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in the i2c core adapter lifetime handling can leave an adapter reachable through i2c_get_adapter while deregistration or registration failure cleanup is tearing down its resources. A local process that can cause or race adapter lookup against adapter removal may obtain a stale reference and trigger access to freed or partially destroyed resources, such as the device name. For the CVSS the PR:L is used for the paranoid score because reliable triggering can involve a local user context with access to I2C adapter interfaces while removal can be caused by hotplug, driver unbind, or system management activity. The issue is not network reachable and requires a local race window, so AC:H is appropriate. Impact is at least local denial of service via kernel crash and in the worst still defensible case may allow confidentiality and integrity impact due to a kernel use-after-free condition.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / Actionable Moderate candidate (with actual score 3)	YES	LOCK USB RACE UAF HARDWARE DEBUGFS LINUS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=4
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 4
* Final recommended bucket: **Borderline manual review recommended / Actionable Moderate candidate**::

## 2. Signal breakdown

* Real lifetime corruption: +1. The adapter can remain reachable in the IDR while deregistration or registration failure cleanup is tearing down resources.
* Memory corruption, weak primitive: +1. The commit explicitly says resources may be accessed after having been freed, but the patch does not show attacker controlled reclaim, overwrite, callback dispatch, type confusion, or refcount takeover.
* Reliable kernel crash / strong DoS: +1 in the paranoid score. A stale adapter lookup during teardown can plausibly lead to an Oops through freed or partially destroyed device resources.
* Local unprivileged trigger: +1 in the paranoid score. A local process may be able to race adapter lookup through I2C-facing interfaces while removal is caused by hotplug, driver unbind, or system management activity.
* Hard or unreliable race: -1. Exploitation requires a narrow timing window between i2c_get_adapter() lookup and adapter deregistration cleanup.
* Requires admin/root for full direct control: applied in conservative interpretation. Directly forcing adapter deregistration or driver unbind normally requires privileged device-management access.

Call-site confidence: medium. The patch shows the lifetime object and IDR removal point, but not all i2c_get_adapter() callers.

## 3. Reachability analysis

The issue is local, not network reachable. A reliable trigger likely needs concurrent adapter lookup and adapter removal. Direct removal is usually privileged through driver unbind, module unload, hotplug, or platform device management. However, the lookup side may be reachable from less privileged local contexts depending on device node permissions and product configuration. Namespaces do not generally make I2C adapter deregistration unprivileged, but container or service models with delegated device access could reduce the practical privilege barrier.

## 4. Severity interpretation

This is not an ordinary bookkeeping fix because the IDR entry can expose an object whose resources are being freed. The realistic impact is local DoS through a race-triggered stale pointer access. The theoretical memory corruption concern is a kernel lifetime bug and UAF-like condition, but the patch does not demonstrate controlled reclaim, writable stale access, type confusion, or callback control. Therefore it is best treated as borderline manual-review material rather than a clear Important-class issue.

## 5. One-sentence report phrase

A race in i2c adapter deregistration can leave an adapter reachable by ID while teardown frees associated resources, allowing a local race to trigger stale resource access and potentially crash the kernel.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: this is a race-dependent lifetime/UAF candidate in a core kernel device subsystem, but the provided patch supports DoS more strongly than privilege escalation.

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

Patch: i2c: core: fix adapter deregistration race
Commit: d39282f552dd6c35b9b84b4af78f1198c24f3373
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d39282f552dd6c35b9b84b4af78f1198c24f3373

Commit description:

Adapters can be looked up by their id using i2c_get_adapter() which
takes a reference to the embedded struct device.

Remove the adapter from the IDR before tearing it down during
deregistration (and on registration failure) to make sure its resources
are not accessed after having been freed (e.g. the device name).

Fixes: 35fc37f ("i2c: Limit core locking to the necessary sections")
Cc: stable@vger.kernel.org	# 2.6.31
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/i2c/i2c-core-base.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=d39282f552dd6c35b9b84b4af78f1198c24f3373

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

The original Linux kernel CVE announcement for CVE-2026-64279 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64279

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:H/PR:L/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:H/I:H/A:H
  The Best / paranoid CVSS score: 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: 2
  Paranoid ActionableScore: 4

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).