[CVE-2026-64035][MODERATE 7.0] igc: set tx buffer type for SMD frames [ Upstream

[CVE-2026-64035][MODERATE 7.0] igc: set tx buffer type for SMD frames [ Upstream

[AL-KERNEL]

CVE: CVE-2026-64035
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: igc: set tx buffer type for SMD frames [ Upstream
Commit: 1f83545f432d106d5fc71d3997b2d382104ebcc4
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1f83545f432d106d5fc71d3997b2d382104ebcc4
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64035
Analysis date: Sun, 19 Jul 2026 16:48:30 -0400
ActionableScore: 6
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A stale TX buffer type in the Intel igc SMD frame path can cause TX completion to use an XDP or XSK cleanup path for an SKB-backed buffer, creating a plausible wrong-free or lifetime-corruption condition with local DoS impact and possible higher impact requiring manual review.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64035 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64035

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-64035	MODERATE	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-843;CWE-763;*CWE-416;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A stale tx buffer type in the igc driver can make SMD frame TX completion use a cleanup path that does not match the object actually stored in the reused descriptor. The affected entry is initialized as an skb but may still carry an older XDP or XSK type, so completion can treat the buffer as the wrong object type and may free or release it incorrectly. For the CVSS the PR:L is used in the paranoid score because reliable triggering may be possible for a local user or service with delegated network administration, XDP, XSK, or reduced capability access rather than only full host root. The issue is not directly network reachable and depends on Intel igc hardware plus frame preemption verification and TX buffer reuse conditions. Impact is at least local denial of service via driver or kernel crash, and in worst case may allow confidentiality or integrity impact due to wrong cleanup path memory corruption. YES REQUIRES MANUAL CHECK.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	REMOTE SIMPLEFIX NETWORK SKB KPANIC  KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=6
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Memory corruption, Weak/indirect corruption candidate: +1
  Stale `igc_tx_buffer->type` can make TX completion interpret an SKB-backed entry as XDP or XSK backed state. This is an object interpretation / cleanup-path mismatch, but the patch does not show attacker-controlled replacement, arbitrary write, or callback control.

* Real lifetime corruption: +1
  The wrong TX completion cleanup path can plausibly release, unmap, or free the wrong object type. This is a lifetime-management concern rather than pure bookkeeping.

* Reliable kernel crash / strong DoS: +1
  A wrong cleanup path in a NIC TX completion path can realistically crash the driver or kernel, even if no exploit primitive is demonstrated.

Conservative deductions / limits:

* Requires admin/root/CAP_NET_ADMIN in typical deployments: -2 considered but not fully dominant in final triage because the bug is in a driver lifetime path and may be reachable through delegated network administration or service-controlled setup.
* No remote/network-triggerable score. The issue is not caused by incoming packets alone.
* No strong LPE score in the conservative result. The patch does not demonstrate reclaim, controlled replacement, write-after-free, function pointer control, or arbitrary write.

Paranoid additional signals:

* Weak LPE concern: +1
  The stale XDP/XSK type can cause cleanup of an object under the wrong semantic type. This is not a proven LPE primitive, but it is enough to justify manual review.

* Privileged kernel/device-management memory corruption path: +1
  The bug is in a trusted NIC driver TX completion ownership path involving SKB/XDP/XSK cleanup semantics.

* Confidentiality impact plausible: +1
  Only for paranoid scoring. If the wrong cleanup path creates a real UAF or object confusion, limited information exposure may become possible.

* Integrity impact plausible: +1
  Only for paranoid scoring. If the wrong cleanup path becomes a real UAF/type confusion primitive, integrity impact cannot be ruled out without completion-path review.

## 3. Reachability analysis

The likely trigger requires Intel `igc` hardware, frame preemption verification / SMD frame handling, and prior reuse of a TX buffer entry that previously carried an XDP or XSK type. Reliable triggering likely requires local control over NIC configuration or related XDP/XSK/FPE setup, commonly requiring root or `CAP_NET_ADMIN`.

Namespaces and containers may matter. If a container root, network-management service, or reduced-capability account has delegated network administration or AF_XDP/XDP-related control, the practical privilege level may be closer to PR:L than full host root.

The path is not directly remotely reachable. Network traffic alone is not enough based on the patch. The exposure is hardware and configuration dependent, but the affected code is in a real NIC driver TX lifecycle path, so it should not be treated as a harmless cleanup-only fix.

Call-site confidence: medium. The provided patch shows only initialization of `buffer->type`, but the commit explicitly states that TX completion can use the wrong cleanup path.

## 4. Severity interpretation

This behaves more like an actionable Moderate than an ordinary Moderate. The realistic impact is probably local DoS through driver or kernel crash under specific hardware/configuration conditions. The theoretical risk is higher because stale object type in a reused TX buffer can turn into wrong free, wrong unmap, UAF, or type confusion depending on TX completion behavior.

It is not a Strong Important candidate by default because the patch does not demonstrate attacker-controlled reclaim, arbitrary write, controlled object replacement, or a practical LPE chain. It should still not be auto-closed because TX completion cleanup-path bugs in network drivers can hide real lifetime corruption.

## 5. One-sentence report phrase

A stale TX buffer type in the Intel igc SMD frame path can cause TX completion to use an XDP or XSK cleanup path for an SKB-backed buffer, creating a plausible wrong-free or lifetime-corruption condition with local DoS impact and possible higher impact requiring manual review.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the patch directly fixes a stale type field that controls cleanup behavior for reused TX buffer entries. Even though exploitation is configuration dependent and not remotely reachable, wrong cleanup paths involving SKB/XDP/XSK ownership are lifetime-sensitive and can plausibly become UAF or type confusion.

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

Patch: igc: set tx buffer type for SMD frames [ Upstream
Commit: 1f83545f432d106d5fc71d3997b2d382104ebcc4
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1f83545f432d106d5fc71d3997b2d382104ebcc4

Changed files:
  drivers/net/ethernet/intel/igc/igc_tsn.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=1f83545f432d106d5fc71d3997b2d382104ebcc4

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

The original Linux kernel CVE announcement for CVE-2026-64035 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64035

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: 3
  Paranoid ActionableScore: 6

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).