[CVE-2026-97436][MODERATE REGULAR] dpaa2-switch: rework FDB management on the bridge leave path [ Upstream

[CVE-2026-97436][MODERATE REGULAR] dpaa2-switch: rework FDB management on the bridge leave path [ Upstream

[AL-KERNEL]

CVE: CVE-2026-97436
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: dpaa2-switch: rework FDB management on the bridge leave path [ Upstream
Commit: abea361a11e4e48695ea149652ef5d3f308b6a49
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=abea361a11e4e48695ea149652ef5d3f308b6a49
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97436
Analysis date: Thu, 24 Sep 2026 17:48:24 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-97436 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97436

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: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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

CVE-2026-97436	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-97436 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N';CWE-284;*CWE-664;CWE-668;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:N';BEST CVSS score: '4.2';DESCR 'A logic error in dpaa2 switch FDB management can cause ports associated with separate Linux bridges to share one forwarding database after a specific bridge leave sequence. Shared FDB state can weaken Layer 2 separation and may result in incorrect MAC learning or frame forwarding between otherwise isolated bridge domains. For the CVSS the PR:N assessment reflects the paranoid case where the invalid shared FDB state was already created by an administrator and an attacker only needs adjacent Layer 2 network access to exploit its effects. The attack requires a specific multi bridge DPSW configuration and bridge membership sequence, so AC:H is appropriate. Impact is limited confidentiality and integrity exposure of network traffic. No memory corruption, kernel crash, or privilege escalation primitive is indicated by the patch.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	YES	REMOTE NETWORK LINUS  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	NO	NO	checked

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

ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: -2
* Conservative score: 0 after lower-bound clamp
* Raw paranoid score: -1
* Paranoid score: 0 after lower-bound clamp
* Final recommended bucket: **Ordinary Moderate**::

The conservative and paranoid scores converge after the supported rare-hardware reduction. The patch establishes an FDB allocation and accounting logic defect, but does not establish memory corruption, a stale object, a direct authorization decision bypass, a demonstrated packet leak, or demonstrated cross-bridge packet forwarding.

2. Signal breakdown

* -2 Rare hardware requirement. The affected path is specific to the NXP DPAA2 hardware switch driver and requires a DPSW instance. This is a material uncommon hardware prerequisite, not merely a generic network-driver classification.
* +0 Direct network reachability not awarded. Network traffic may be affected after an invalid FDB sharing state exists, but an attacker-controlled packet does not directly invoke the vulnerable bridge-leave FDB allocation path.
* +0 Local unprivileged trigger not awarded. The supplied evidence does not show that an ordinary user can create the required multi-bridge DPSW configuration or perform the complete bridge-leave sequence.
* +0 Security-boundary bypass not awarded conservatively. Separate Linux bridges normally represent separate Layer 2 domains, and shared FDB state may weaken that separation. However, the supplied patch does not demonstrate that a frame is forwarded across bridges, disclosed to another bridge, or injected into another bridge.
* +1 Potential Layer 2 isolation concern awarded only in the paranoid interpretation. The driver allocates FDBs so that standalone ports have private FDBs, and the bug can cause multiple ports to share an FDB after a specific topology sequence. This creates a technically defensible concern for incorrect MAC learning or forwarding-domain confusion, but not a demonstrated authorization bypass.
* +0 Memory corruption signals. No UAF, double free, refcount mutation, OOB access, stale pointer dereference, DMA overwrite, or controlled write is established.
* +0 Availability signals. The patch does not establish a host crash, kernel panic, device reset, or persistent resource exhaustion.

3. Reachability analysis

The vulnerable operation is performed when a DPAA2 switch port leaves a Linux bridge. Reaching the FDB-management operation requires control-plane changes to bridge membership, a multi-bridge topology using ports from the same DPSW instance, and a sequence that leaves an FDB incorrectly marked as in use.

The complete required privilege boundary is not visible in the supplied context. Linux bridge configuration generally requires CAP_NET_ADMIN, but the patch does not establish whether the relevant DPAA2 switch ports and all required bridge operations are controlled in the initial host namespace, a delegated network namespace, or another management domain. Therefore HostAdminRequired and NamespaceScopedPrivilege are UNKNOWN.

An adjacent Layer 2 attacker could potentially benefit after the invalid shared-FDB state has already been created. However, the supplied evidence does not establish that this attacker can create that state, force bridge membership changes, or reliably cause cross-bridge forwarding. No prior privileged setup is proven as part of a complete exploit chain, but the required specialized DPSW hardware and multi-bridge configuration are material prerequisites.

4. Primitive and severity interpretation

The established primitive is an FDB lifecycle and allocation-state bookkeeping error. When the last port leaves one bridge, the old FDB may remain marked as used even though it should become reusable. Repeated bridge topology changes can then exhaust the available FDB allocation model and cause separate ports to share an FDB.

This is not a memory-lifetime violation. There is no freed object, stale reference, post-free use, refcount operation, active-object corruption, or repeated release operation. The patch does not establish an attacker-controlled packet payload reaching an unsafe memory operation.

The likely operational consequence is incorrect Layer 2 forwarding-domain behavior on affected DPAA2 switch hardware. Incorrect shared FDB state may plausibly cause MAC-learning interference or forwarding confusion between ports expected to have distinct FDBs. That consequence requires validation against DPAA2 hardware forwarding semantics and the surrounding driver code before treating it as a confidentiality, integrity, or security-boundary issue.

PrimitiveClass is NONE because the supplied evidence establishes no concrete corruption, lifetime, authorization, or demonstrated isolation-bypass primitive. ImportantCandidate is NO because the potential security consequence remains dependent on unproven hardware forwarding behavior. AutoDowngradeAllowed is YES because no unresolved concrete corruption or access-control primitive would be lost by ordinary triage handling.

5. One-sentence report phrase

A DPAA2 switch FDB allocation logic error can cause ports from separate bridge configurations to share an FDB after specific bridge leave operations, potentially affecting Layer 2 forwarding isolation on affected hardware.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Verify whether shared DPSW FDB instances can actually learn or forward MAC traffic across separate Linux bridge domains, and determine whether the required bridge configuration can be created by a delegated CAP_NET_ADMIN actor rather than only by host network administration.

7. Call-site confidence

Call-site confidence: medium

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

Patch: dpaa2-switch: rework FDB management on the bridge leave path [ Upstream
Commit: abea361a11e4e48695ea149652ef5d3f308b6a49
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=abea361a11e4e48695ea149652ef5d3f308b6a49

Changed files:
  drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.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=abea361a11e4e48695ea149652ef5d3f308b6a49

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

The original Linux kernel CVE announcement for CVE-2026-97436 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97436

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:L/I:L/A:N
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
  The Best / paranoid CVSS score: 4.2

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: 0

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).