[CVE-2025-38425][MODERATE 7.0] i2c: tegra: check msg length in SMBUS block read [ Upstream

[CVE-2025-38425][MODERATE 7.0] i2c: tegra: check msg length in SMBUS block read [ Upstream

[AL-KERNEL]

CVE: CVE-2025-38425
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: i2c: tegra: check msg length in SMBUS block read [ Upstream
Commit: c39d1a9ae4ad66afcecab124d7789722bfe909fa
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c39d1a9ae4ad66afcecab124d7789722bfe909fa
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2025-38425
Analysis date: Tue, 13 Oct 2026 11:25:42 -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-2025-38425 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2025-38425

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-2025-38425	MODERATE	https://www.kernelcve.org/list/?q=CVE-2025-38425 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=MODERATE_KPANIC RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-20;CWE-130;*CWE-787;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '6.8';DESCR 'i2c tegra SMBus block read invalid length I2C_M_RECV_LEN I2C_SMBUS_BLOCK_MAX out_of_bounds_write memory_corruption kernel_panic physical_device';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	MAYBE	USB SIMPLEFIX HARDWARE LINUS  KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4	-	-	checked

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

ActionableScore=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 5
* Raw paranoid score: 1
* Paranoid score: 5
* Applied conservative manual-review safety floor: 1 -> 5 because an attacker-influenced kernel OOB write is established.
* Applied paranoid manual-review safety floor: 1 -> 5 for the same primitive. No extra speculative leverage was added.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +2 Strong corruption primitive. The device-provided length expands `msgs[i].len` beyond `I2C_SMBUS_BLOCK_MAX`, after which the driver performs another receive into the caller-provided buffer. A controlled peripheral can influence both the excessive length and transferred bytes.
* +1 Reliable kernel crash or strong DoS. An oversized transfer can overwrite memory beyond the SMBus receive buffer and plausibly cause a kernel fault.
* -2 Physical or peripheral-control prerequisite. Exploitation requires control of a device on the Tegra I2C or SMBus bus, or equivalent compromise of that peripheral. No direct local-userspace or network path is established.
* No UAF or lifetime signal applies.
* No confidentiality or integrity bonus was awarded. The OOB write is concrete, but no adjacent victim, directed target, protected object, disclosure, or privilege-escalation chain is established.
* No arbitrary-write bonus beyond the strong OOB primitive was awarded. The destination begins immediately after a fixed receive buffer, and arbitrary target selection is not shown.
* No additional availability point was awarded because it would duplicate the same possible kernel crash.
* B5-R is not established. The patch shows neither retry-accumulated indexing nor corrupted descriptor consumption across retries.
* B3-PENDING is not established because no shared or file-backed storage is involved.
* B4-PENDING is not applicable because this is not an authorization decision bug.

3. Reachability analysis

The untrusted value originates from an I2C or SMBus peripheral during a block-read transaction. A malicious peripheral can return zero or a value above 32 in the length byte. Before the fix, the driver adds that value to the transfer length and proceeds with the remaining read.

No ordinary local-user interface, network trigger, namespace capability, or host UID requirement is established by the supplied evidence. The complete trigger also depends on the host initiating the relevant SMBus block read, and the supplied call path does not identify who can cause that operation. Therefore `HostAdminRequired` and `RequiresHostUID0` remain unknown rather than being assumed either required or unnecessary.

The operation is hardware-specific to Tegra I2C and is not namespace-scoped. No race or timing window is involved. Physical peripheral control or peripheral firmware compromise is the material exposure prerequisite.

4. Primitive and severity interpretation

The exact primitive is an attacker-influenced OOB write caused by accepting a device-supplied SMBus block length greater than the protocol maximum. The subsequent transfer writes additional device-controlled bytes beyond the expected receive-buffer boundary.

This is `CLASS_A` because a real, attacker-influenced kernel write outside the intended buffer is established. It is not a UAF, retry-accumulated B5-R case, authorization bypass, or shared-backing ownership violation.

The demonstrated practical consequence is memory corruption with plausible kernel crash or DoS. Arbitrary target selection, controlled replacement, disclosure, credential modification, and LPE remain unproven. The exact storage class of every possible caller buffer is not shown, so the narrower claim of a confirmed heap or slab overwrite is not made.

`ImportantCandidate=YES` and `AutoDowngradeAllowed=NO` because automatically reducing a concrete peripheral-controlled OOB write to ordinary Moderate could discard meaningful unresolved exploitation leverage. The physical exposure limitation reduces practical reachability but does not turn the write into a parser-only or crash-only defect.

5. One-sentence report phrase

A malicious I2C peripheral can supply an oversized SMBus block length that causes the Tegra driver to receive device-controlled bytes beyond the expected buffer, creating a kernel OOB write with potential crash and unresolved corruption impact.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Confirm the receive-buffer allocation at all `I2C_M_RECV_LEN` call sites, the maximum PIO or DMA transfer size, overwrite extent, and whether any realistic peripheral or firmware threat model provides repeatable triggering.

7. Call-site confidence

Call-site confidence: medium

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

Patch: i2c: tegra: check msg length in SMBUS block read [ Upstream
Commit: c39d1a9ae4ad66afcecab124d7789722bfe909fa
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c39d1a9ae4ad66afcecab124d7789722bfe909fa

Changed files:
  drivers/i2c/busses/i2c-tegra.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=c39d1a9ae4ad66afcecab124d7789722bfe909fa

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

The original Linux kernel CVE announcement for CVE-2025-38425 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2025-38425

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:P/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 6.8

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: 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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).