* [CVE-2026-93283][MODERATE 7.0] i3c: master: Fix device_register() error path [ Upstream
@ 2026-09-24 21:56 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-24 21:56 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-93283
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: i3c: master: Fix device_register() error path [ Upstream
Commit: 5bf498623f8397d45f85f14cd631c5e5a565c2fb
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5bf498623f8397d45f85f14cd631c5e5a565c2fb
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93283
Analysis date: Thu, 24 Sep 2026 17:56:36 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
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-2026-93283 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93283
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-2026-93283 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-93283 CHECK WITH IMPACT FROM ORIG NN LOW 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-416;CWE-825;*CWE-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'An error path in i3c_master_register_new_i3c_devs can free an i3c_device through put_device while desc dev still points to the released object. A later cleanup operation such as i3c_master_unregister_i3c_devs can treat the stale pointer as valid and dereference the freed object, resulting in a use after free and at least a kernel crash. For the CVSS the PR:L value is used for the paranoid score because a reduced capability service, container, or delegated device management process may be able to trigger device registration failure and later teardown without having unrestricted host administrator privileges. The attack is not network reachable and normally requires local device management access or influence over the I3C device lifecycle. Impact is at least a local denial of service via kernel crash and in the worst case may affect confidentiality and integrity if the freed device object is reused before stale device cleanup operations access it. This memory corruption path should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) SKIP CVE-2026-93283 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE LEAK ERRORPATH UAF HARDWARE KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
1. ActionableScore
* Raw conservative score: 4
* Conservative score: 5
* Raw paranoid score: 5
* Paranoid score: 5
* Applied conservative floor: 4 -> 5 under the concrete repeated release or refcount UAF floor.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
* +2 Real UAF. A failed `device_register()` is followed by `put_device()`, which drops the final reference and frees the `i3c_device`, while `desc->dev` retains the freed address.
* +1 Concrete repeated release or refcount operation. The exact stale `desc->dev` can later reach `i3c_master_unregister_i3c_devs()`, where normal `device_unregister()` semantics include device teardown and another `put_device()` on the embedded `struct device`.
* +1 Reliable kernel crash or strong DoS. Dereferencing or unregistering the freed device can produce an invalid access, refcount corruption, or kernel fault.
* +1 Paranoid repeated-refcount leverage. The later unregister operation can perform write-like device, kobject, and reference-lifetime mutations through storage whose original object lifetime has ended. This is scored only in the paranoid arithmetic.
* No negative privilege penalty. Host-admin-equivalent privilege is not established by the supplied evidence.
* No race penalty. This is an ordered error and cleanup sequence, not a timing race.
* No hardware rarity penalty. I3C hardware is required, but the evidence does not establish rare or physical-attacker-only conditions.
* Controlled reclaim, attacker-shaped replacement contents, arbitrary read or write, callback control, disclosure, and privilege escalation are not demonstrated.
* Structured stale-object leverage is not separately awarded. The meaningful stale operation is already represented by the concrete repeated lifetime mutation.
* Weak LPE is not separately awarded for the same repeated-release fact.
* No extra Availability point is awarded because it would duplicate the kernel-crash consequence.
* Confidentiality and integrity points are not awarded merely because the second release could theoretically touch reclaimed memory.
* First release can end lifetime: yes. The commit explicitly says the final reference is dropped and `i3c_device_release()` frees the object.
* Exact reference survives: yes. `desc->dev` remains non-NULL and retains the freed address.
* Second lifetime mutation is concrete: yes, assuming the documented later unregister path reaches normal `device_unregister()` lifetime handling.
* Concrete repeated release or refcount +1 awarded: yes.
* Paranoid repeated-refcount leverage +1 awarded: yes.
* FLOOR 5 applied: yes, to the conservative score.
3. Reachability analysis
The failure occurs while the I3C master registers newly discovered devices. An attacker would need to induce a `device_register()` failure and later cause or await master-device cleanup. The supplied evidence does not establish whether an ordinary local user, delegated service, malicious peripheral, firmware, or only a host administrator can complete that sequence, so `HostAdminRequired` remains UNKNOWN and no privilege bonus or penalty is applied.
I3C device registration is not an attacker-created user or network namespace operation, so the complete trigger is not namespace scoped. Prior availability of an I3C controller and device-discovery activity is required. Direct network reachability is not established. Peripheral or firmware influence is possible in principle but is not sufficiently demonstrated for a firmware-mediated exposure point. No timing race is required because the stale pointer results directly from the failed registration error path and survives until later unregister processing.
4. Primitive and severity interpretation
The exact primitive is a stale pointer to a freed active structured `i3c_device`, including its embedded `struct device`. This is not fixed stale storage. The first `put_device()` can and, according to the commit, does invoke the release callback and free the object.
The later path is primarily cleanup or unregister processing, but it is stronger than an ordinary stale cleanup read. It can pass the same dangling device reference into an operation that tears down device-core state and ultimately mutates its lifetime reference again. This is category B, a second lifetime or refcount mutation through a potentially dangling object, rather than category A, a shallow stale dereference only.
The primitive is CLASS_B. A crash or host DoS is the demonstrated practical consequence. Controlled reclaim, arbitrary kernel access, callback hijacking, and privilege escalation remain speculative. CLASS_A is therefore not justified.
`ImportantCandidate=YES` because the concrete second lifetime mutation leaves unresolved whether reused storage can be modified through device-core or refcount processing. `AutoDowngradeAllowed=NO` because automatically treating this as an ordinary cleanup crash would discard the established repeated lifetime-corruption mechanism. Operationally, it is Actionable Moderate at minimum, with Important classification dependent on reachability and post-free behavior.
5. One-sentence report phrase
A failed I3C device registration frees the i3c_device while leaving desc dev dangling, allowing later unregister processing to dereference and potentially perform another lifetime mutation on the freed device, causing at least a kernel crash and requiring manual exploitation-leverage review.
6. Manual review recommendation
MANUAL CHECK REQUIRED
Verify who can reliably induce `device_register()` failure, whether the later unregister path reaches `device_unregister()` before faulting, and whether allocator reuse permits device-core or refcount mutations against replacement storage.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: i3c: master: Fix device_register() error path [ Upstream
Commit: 5bf498623f8397d45f85f14cd631c5e5a565c2fb
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5bf498623f8397d45f85f14cd631c5e5a565c2fb
Changed files:
drivers/i3c/master.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=5bf498623f8397d45f85f14cd631c5e5a565c2fb
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-93283 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93283
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: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: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: unknown
Paranoid ActionableScore: 5
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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