[CVE-2026-90079][MODERATE REGULAR] octeontx2-af: fix cn20k mailbox lifetime on repeated rvu_mbox_init() [ Upstream

[CVE-2026-90079][MODERATE REGULAR] octeontx2-af: fix cn20k mailbox lifetime on repeated rvu_mbox_init() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-90079
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: octeontx2-af: fix cn20k mailbox lifetime on repeated rvu_mbox_init() [ Upstream
Commit: a0fcbea79f034f49bdd44915f28938922023458d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a0fcbea79f034f49bdd44915f28938922023458d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90079
Analysis date: Thu, 17 Sep 2026 14:31:39 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-90079 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90079

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.

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

CVE-2026-90079	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-90079 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	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-401;CWE-667;*CWE-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'Repeated rvu_mbox_init calls can overwrite the stored ng_rvu allocation and leak the object created for the AF-PF mailbox path. More importantly, an AF-VF initialization failure can release shared CN20k mailbox DMA memory while active AF-PF mailbox handlers may still use it, creating a potential use-after-free condition. Reinitializing mbox_lock while an AF-PF handler may hold the mutex can also invalidate synchronization and increase the risk of memory lifetime violations. For the CVSS the PR:L reflects the paranoid case where SR-IOV or VF management is delegated to a reduced capability service account, container root, or virtualization operator rather than requiring unrestricted host root. AC:H applies because the security relevant outcome depends on a failed initialization or teardown sequence and possible concurrency with active mailbox handling. The issue is not directly network reachable through ordinary Ethernet traffic. Impact is at least a local denial of service through a kernel crash and in the worst defensible case may include confidentiality and integrity impact because active handlers can retain access to released DMA backed mailbox memory. Manual review is required to determine whether a controlled VF or delegated SR-IOV user can reliably reach the failure path and influence the released memory.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)  SKIP CVE-2026-90079 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	REMOTE INIT NOMEMCHK LEAK ERRORPATH UAF NETWORK DMAorINTERRUPT LINUS  LOWERED_FROM_HIGH_BASED_ON_NULLPTR DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	-	-	checked

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

ActionableScore=3
ActionableScoreLower=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 3
* Paranoid score: 3
* No floor or cap was applied.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

Conservative signals:

* +1 Concrete persistent kernel resource leak. Repeated `rvu_mbox_init()` overwrites `rvu->ng_rvu`, losing the first `ng_rvu` allocation, and some failure paths omit CN20k mailbox DMA cleanup.
* +1 Weak active-state corruption concern. Reinitializing `mbox_lock` while an AF-PF handler may hold it can invalidate mutex state and mutual exclusion.
* Total: 2.

Paranoid-only signal:

* +1 Realistic kernel crash or strong DoS. Concurrent use of a reinitialized mutex or incorrectly unwound mailbox state can plausibly produce a kernel fault, deadlock, or driver failure, although the supplied evidence does not document an observed crash.
* Total: 3.

Not awarded:

* Real UAF +2 was not awarded. In the shown pre-patch code, each invocation allocates a separate `ng_rvu`. The dangerous freeing of live AF-PF DMA described in the commit is a teardown problem that would be exposed when changing to a shared `ng_rvu`, but the same patch prevents that condition by introducing type-specific cleanup.
* A stale global `rvu->ng_rvu` may remain after `kfree()` on an initialization error, but no subsequent dereference of that exact pointer is visible or directly established in the supplied context.
* No concrete repeated release or refcount mutation exists. The first free and a later second lifetime mutation on the exact same reference are not established.
* Structured stale-object leverage, controlled reclaim, arbitrary write, attacker-controlled DMA reuse, confidentiality impact, integrity impact, and privilege escalation were not demonstrated.
* Remote reachability was not awarded. Ordinary Ethernet traffic does not directly invoke `rvu_mbox_init()` or enable SR-IOV.
* Firmware-mediated influence was not awarded because attacker control of firmware or mailbox initialization failure is not established.
* No extra Availability point was awarded beyond the paranoid crash signal.
* FLOOR 4 and FLOOR 5 were not applied because an actual stale post-lifetime use is not established.

3. Reachability analysis

The affected path is specific to Marvell CN20k RVU mailbox initialization. AF-PF initialization occurs during device probe, while AF-VF initialization occurs when SR-IOV is enabled.

Enabling SR-IOV is normally a host device-management operation, but the supplied call sites do not prove whether every vulnerable sequence requires a host administrator or whether probe-time configuration can reach related failure paths automatically. Therefore, `HostAdminRequired` remains `UNKNOWN`, and no privilege penalty is applied.

No evidence shows that the complete operation is available through an attacker-created user or network namespace. `NamespaceScopedPrivilege` is therefore `UNKNOWN`.

The path requires compatible CN20k hardware and the affected driver. No hardware rarity penalty is applied merely because this is driver-specific. There is no demonstrated remotely controlled trigger, VF-to-PF exploit sequence, or repeatable below-host-admin method for forcing the relevant allocation failure.

The mutex issue has a concurrency component, but no timing penalty is applied because the commit does not establish that the interleaving is narrow, one-shot, or difficult to reproduce.

4. Primitive and severity interpretation

The established defects are a persistent allocation/DMA cleanup leak and unsafe reinitialization of an active mutex. These are primarily resource-lifetime and invalid-synchronization problems.

The supplied diff does not directly establish that pre-patch code frees AF-PF mailbox DMA and then allows an AF-PF handler to use that same freed allocation. The old implementation creates separate `ng_rvu` objects for the AF-PF and AF-VF calls. Sharing the object would expose the cross-type teardown problem, and the patch introduces sharing together with type-specific cleanup.

Accordingly, this is not classified as a proven active-object UAF. It is `CLASS_C`, representing invalid active state and potential DoS without an independently useful corruption primitive.

A crash, deadlock, or device failure is technically plausible from mutex corruption or inconsistent teardown. Controlled reclaim, post-free DMA corruption, arbitrary read or write, information disclosure, and privilege escalation are not established.

`ImportantCandidate=NO` because no Class A primitive or sufficiently strong Class B lifetime primitive is demonstrated. `AutoDowngradeAllowed=YES` because the evidence supports a constrained driver initialization and cleanup defect rather than unresolved attacker-useful kernel corruption.

Operational severity is Low to Moderate, with manual review appropriate to verify whether omitted CN20k mailbox handlers dereference `rvu->ng_rvu` after the AF-VF failure path.

5. One-sentence report phrase

Repeated CN20k mailbox initialization can leak allocations and reinitialize an active mutex, potentially causing resource loss, deadlock, or a kernel or driver failure during probe or SR-IOV setup.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Review AF-PF mailbox handler call sites after AF-VF initialization failure to determine whether they subsequently dereference the freed `rvu->ng_rvu` object or access DMA memory released through the shared cleanup path, which would upgrade the issue to a real Class B UAF.

7. Call-site confidence

Call-site confidence: medium

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

Patch: octeontx2-af: fix cn20k mailbox lifetime on repeated rvu_mbox_init() [ Upstream
Commit: a0fcbea79f034f49bdd44915f28938922023458d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a0fcbea79f034f49bdd44915f28938922023458d

Changed files:
  drivers/net/ethernet/marvell/octeontx2/af/cn20k/api.h
  drivers/net/ethernet/marvell/octeontx2/af/cn20k/mbox_init.c
  drivers/net/ethernet/marvell/octeontx2/af/rvu.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=a0fcbea79f034f49bdd44915f28938922023458d

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

The original Linux kernel CVE announcement for CVE-2026-90079 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90079

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: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: 3

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).