[CVE-2026-74725][MODERATE 7.0] enic: fix tx_hang_reset use-after-free on device removal [ Upstream

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-74725
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: enic: fix tx_hang_reset use-after-free on device removal [ Upstream
Commit: 8619865f34fb3b130b567855382a5c4aadd522b9
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8619865f34fb3b130b567855382a5c4aadd522b9
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74725
Analysis date: Sat, 22 Aug 2026 12:35:23 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum / manual review required
Manual review required: YES

Summary:
A race in the ENIC device removal path can allow `tx_hang_reset` work to be requeued and executed after `free_netdev()`, causing a use-after-free that is realistically a privileged local DoS and warrants manual review for possible memory corruption impact.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-74725 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74725

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-2026-74725	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:H/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'An enic teardown race can cause a use after free when a TX timeout schedules enic_tx_hang_reset while the PCI device is being removed. The work item may run after free_netdev and access netdev private memory that has already been freed, which can crash the kernel and represents a memory corruption class bug. For the CVSS the PR:H because reliable triggering normally requires administrative control over device removal, driver unbind, or a comparable teardown path on the victim. The issue is not directly network reachable because packet traffic alone is not enough to remove the device, although TX timeout timing can be influenced by device or network conditions during teardown. Impact is at least denial of service via kernel crash. For the paranoid score, CIA:H,H,H is kept as the highest still defensible interpretation because the patch context explicitly identifies a use after free after free_netdev, so privilege escalation cannot be ruled out without manual review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum / manual review required (with actual score 4)	YES	REMOTE RACE UAF NETWORK HARDWARE LINUS  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum / manual review required**::

## 2. Signal breakdown

Conservative signals:

* Memory corruption, weak primitive: +1
  The commit explicitly describes a use-after-free after `free_netdev()`, but it is race-dependent and does not show attacker-controlled reclaim, overwrite, type confusion, callback control, or refcount takeover.

* Real lifetime corruption: +1
  `tx_hang_reset` can survive teardown and run after the associated `netdev` memory has been freed.

* Reliable kernel crash / strong DoS: +1
  A work item accessing freed `netdev` private memory can plausibly crash the kernel.

* Privileged kernel/device-management memory corruption path: +1
  The bug is in a NIC driver teardown path involving workqueue lifetime and device removal.

* Requires admin/root/CAP_* in typical deployments: -2
  Reliable triggering normally requires PCI device removal, driver unbind, hot-unplug control, or comparable administrative teardown.

* Hard or unreliable race / special timing required: -1
  The TX timeout must race with device removal and workqueue teardown.

* Hardware/device-specific exposure: -1
  The affected path requires Cisco ENIC hardware or a matching virtual/device environment.

Paranoid additions/interpretation:

* Weak LPE concern: +1
  Because the primitive is a real UAF after `free_netdev()`, privilege escalation cannot be fully ruled out without allocator and call-site review, even though no reclaim primitive is demonstrated.

* Firmware-mediated or device/network-influenced timing: +1
  TX timeout behavior may be influenced by device or network conditions, but this is not the same as a directly network-triggerable vulnerability.

The paranoid score is capped at 5 by the race-UAF downgrade rule because the patch shows a stale work item after free, but not controlled reuse, write-after-free, callback hijack, or arbitrary memory access.

## 3. Reachability analysis

The bug is triggered during ENIC device removal while a TX timeout can still schedule `enic_tx_hang_reset()`. In normal deployments, removing or unbinding the device is an administrative operation, so the practical PR is high. A local unprivileged user cannot normally trigger the teardown path directly.

Network traffic alone is not sufficient because packet traffic does not remove the PCI device. However, traffic or device conditions may influence TX timeout timing once teardown is already in progress. Namespaces and containers usually do not lower the requirement unless a container or service account has delegated control over device unbind, PCI hotplug, or privileged network device management.

Call-site confidence: high. The patch directly changes `enic_remove()` and the commit explains the workqueue requeue window leading to use-after-free after `free_netdev()`.

## 4. Severity interpretation

This is more than an ordinary Moderate cleanup because the commit explicitly identifies a use-after-free in a kernel driver teardown path. Realistic exploitation most likely behaves as a privileged local DoS through kernel crash. Theoretical privilege escalation is not strongly supported because there is no shown attacker-controlled reclaim, stale callback target, type confusion, or write primitive.

Therefore, the conservative score remains borderline, but the paranoid score reaches Actionable Moderate because kernel UAF lifetime bugs should not be auto-closed without manual review.

## 5. One-sentence report phrase

A race in the ENIC device removal path can allow `tx_hang_reset` work to be requeued and executed after `free_netdev()`, causing a use-after-free that is realistically a privileged local DoS and warrants manual review for possible memory corruption impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the patch explicitly fixes a use-after-free after `free_netdev()` in an asynchronous workqueue teardown path. Even though the practical trigger appears privileged and race-dependent, UAF lifetime bugs in driver teardown should be manually reviewed before closure.

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

Patch: enic: fix tx_hang_reset use-after-free on device removal [ Upstream
Commit: 8619865f34fb3b130b567855382a5c4aadd522b9
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8619865f34fb3b130b567855382a5c4aadd522b9

Changed files:
  drivers/net/ethernet/cisco/enic/enic_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=8619865f34fb3b130b567855382a5c4aadd522b9

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

The original Linux kernel CVE announcement for CVE-2026-74725 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74725

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:H/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 6.4

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: 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: NO
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).