* [CVE-2026-99028][MODERATE 7.0] net: xilinx: axienet: Free outstanding DMA buffers on dmaengine stop [ Upstream
@ 2026-10-27 1:02 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-27 1:02 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-99028
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: net: xilinx: axienet: Free outstanding DMA buffers on dmaengine stop [ Upstream
Commit: 079396129da5e7cb40ca0920aa1b9525bef6097c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=079396129da5e7cb40ca0920aa1b9525bef6097c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99028
Analysis date: Mon, 26 Oct 2026 21:02:36 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
A shutdown-versus-RX-completion race can leave DMA and callback state active after descriptor teardown, alongside persistent SKB/DMA-mapping leaks.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99028 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99028
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-2026-99028 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99028 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE_KPANIC RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE_KPANIC) 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-401;CWE-459;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'The dmaengine teardown path has both a persistent resource leak and a race based memory corruption candidate. A receive completion can resubmit a DMA mapped buffer around interface shutdown, after which teardown may free the SKB while the DMA engine can still write into its former storage. This is a DMA write into freed memory and may cause a kernel crash or corrupt a reallocated kernel object, although reliable privilege escalation is not demonstrated. For the CVSS the PR:L paranoid value represents a delegated network administrator, container service, or reduced capability process that can stop the affected interface without having unrestricted host root access. AC:H reflects the need to overlap RX completion and interface teardown. The issue is not directly remotely exploitable because network traffic can stimulate completions but a privileged control plane action is still needed to invoke ndo_stop. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 5 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were INCREASED_TO_HIGH_BASED_ON_GUESSCVSS and LOWERED_FROM_HIGH_BASED_ON_NULLPTR. The independent weaker Aegis shadow evaluated CVSS 1.9 and ActionableScore 1 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) MAYBE REMOTE LOCK INIT RACE LEAK UAF NETWORK SKB DMAorINTERRUPT HARDWARE KPANIC MEMORY KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS KPANIC LOWERED_FROM_HIGH_BASED_ON_NULLPTR - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 4.
* Conservative score: 4; no floor or cap changed it.
* Raw paranoid score: 5.
* Paranoid score: 5; no floor or cap changed it.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
* +2 — Real asynchronous lifetime violation: RX completion can resubmit after termination, while teardown frees ring descriptor shells still referenced by the DMA transaction/callback.
* +1 — Reliable kernel crash/strong DoS is plausible when a later completion consumes the freed structured descriptor.
* +1 — Concrete persistent resource leak: outstanding SKBs and DMA mappings are lost on each interface shutdown and can exhaust a limited IOMMU aperture.
* Paranoid +1 — The commit explicitly describes DMA continuing to write after teardown frees its buffer. This is a technically defensible post-free write concern, but the visible parent code leaks rather than frees the SKB itself, so the exact freed DMA target is not fully demonstrated by the diff.
* No race penalty: concurrency is required, but the evidence does not establish narrow, one-shot, or materially uncontrollable timing.
* No hardware/rarity penalty: Xilinx dmaengine hardware is required, but rarity or physical attacker access is not established.
* No controlled reclaim, arbitrary target, callback control, disclosure, LPE, or C/I impact is shown.
* Extra Availability was not awarded for the same possible crash.
* NEW52/B5-R does not apply: there is no retry-accumulated index or heap OOB write.
* B3-PENDING and B4-PENDING do not apply.
3. Reachability analysis
The vulnerable transition is `ndo_stop()` on a Xilinx AXI Ethernet interface concurrent with RX completion. Stopping an interface normally requires network-management authority, but the evidence does not identify whether the relevant device can be controlled with delegated/net-namespace CAP_NET_ADMIN or requires host administration over a host-owned physical device. Thus both effective host-admin and namespace-scoped reachability remain unknown. Network traffic may stimulate completions, but cannot alone invoke shutdown. No proof establishes a normal unprivileged or directly remote complete trigger.
4. Primitive and severity reading
The conservative primitive is an active structured DMA-descriptor UAF: a resubmitted transaction can retain callback state after its ring descriptor shell is freed. This is broader than a harmless leak, but controlled replacement or useful stale-field consumption is not shown. The stronger commit-described primitive is a fixed stale DMA write into freed buffer storage; the supplied diff does not fully reconcile that claim because the old teardown fails to free the SKB.
This remains CLASS_B, not CLASS_A. ImportantCandidate is YES because unresolved asynchronous DMA ownership and active callback-state corruption require exploit-leverage review. Auto-downgrade is disallowed because the post-teardown DMA/callback lifetime path is concrete, even though Important severity and privilege escalation are unproven.
5. One-sentence report phrase
A shutdown-versus-RX-completion race can leave DMA and callback state active after descriptor teardown, alongside persistent SKB/DMA-mapping leaks.
6. Manual review advice
MANUAL CHECK REQUIRED
Confirm the submitted descriptor’s callback context and DMA destination lifetime, plus the capability namespace governing interface shutdown.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: net: xilinx: axienet: Free outstanding DMA buffers on dmaengine stop [ Upstream
Commit: 079396129da5e7cb40ca0920aa1b9525bef6097c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=079396129da5e7cb40ca0920aa1b9525bef6097c
Changed files:
drivers/net/ethernet/xilinx/xilinx_axienet.h
drivers/net/ethernet/xilinx/xilinx_axienet_main.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=079396129da5e7cb40ca0920aa1b9525bef6097c
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99028 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99028
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: 4
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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