[CVE-2026-45891][MODERATE 7.0] net: hns3: fix double free issue for tx spare buffer [ Upstream

[CVE-2026-45891][MODERATE 7.0] net: hns3: fix double free issue for tx spare buffer [ Upstream

[AL-KERNEL]

CVE: CVE-2026-45891
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net: hns3: fix double free issue for tx spare buffer [ Upstream
Commit: fb6a4c376d454b425555b1b0bda36e99f56ec307
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fb6a4c376d454b425555b1b0bda36e99f56ec307
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45891
Analysis date: Wed, 27 May 2026 09:37:13 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-45891 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45891

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-2026-45891	MODERATE	CHECK	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-415;*CWE-416;*CWE-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'hns3 can keep a stale tx_spare pointer during ring parameter reconfiguration rollback. If new tx_spare allocation fails and hns3_init_all_ring enters its cleanup path, the stale pointer can be treated as a newly allocated buffer and freed again, causing a double free in the network driver. For the CVSS the PR:L is used for the paranoid case because delegated CAP_NET_ADMIN, containerized network administration, or a reduced privilege service account may be able to trigger ring parameter changes without full host root. Reliable exploitation still requires a local device management path and an allocation failure window. The issue is not network reachable. Impact is at least local denial of service via kernel crash and in the paranoid interpretation may include confidentiality and integrity impact due to kernel double free memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	REMOTE INIT ERRORPATH UAF NETWORK PACKET  DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7 DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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

ActionableScore=5
ActionableScoreLower=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

2. Signal breakdown
* Generic memory corruption / double-free: +2. The commit explicitly states that a stale `tx_spare` pointer can be freed twice.
* Real lifetime corruption: +1. The stale pointer comes from rollback state and is later interpreted as a live newly allocated buffer.
* Reliable kernel crash / strong DoS: +1. Double-free in a network driver cleanup path can realistically crash or destabilize the kernel.
* Weak LPE concern: +1 in paranoid scoring. Double-free is a risky memory corruption class, but no controlled reclaim, payload control, or arbitrary write primitive is demonstrated.
* Privileged kernel/device-management path: +1. The affected path is NIC ring parameter reconfiguration and error cleanup.
* Requires CAP_NET_ADMIN or equivalent in typical deployments: -2. Reliable triggering normally requires ethtool/ringparam or device-management privileges.
* Hard or constrained trigger: -1. The bug also depends on allocation failure or failed tx_spare initialization during reconfiguration.
* Not network reachable: +0. Packet traffic alone is not the trigger.

3. Reachability analysis
The likely trigger is local network-device management, such as changing ring parameters through ethtool or equivalent control paths on systems using the hns3 driver. In typical host deployments this requires CAP_NET_ADMIN. In containers or delegated network-management environments, a reduced-privilege service account or container root may have enough authority to trigger ringparam changes without full host root, which supports the paranoid PR:L interpretation. Exploitation also needs the allocation failure or initialization-failure path, making reliability lower. The issue is not remotely reachable through normal packet traffic.

4. Severity interpretation
This is more serious than an ordinary Moderate because the bug is an explicit double-free in kernel driver memory management. Realistic evidence supports local DoS under constrained conditions. Privilege escalation is not proven, but double-free bugs are historically risky and should not be auto-closed, especially when delegated CAP_NET_ADMIN may expose the path to less trusted actors.

5. One-sentence report phrase
hns3 ring parameter rollback can leave a stale `tx_spare` pointer that is later freed again on allocation-failure cleanup, causing a local double-free in the network driver.

6. Manual review recommendation
MANUAL CHECK REQUIRED
The patch fixes an explicit double-free, and although triggering requires local device-management privileges plus an allocation-failure path, the memory corruption class warrants manual triage.

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

Patch: net: hns3: fix double free issue for tx spare buffer [ Upstream
Commit: fb6a4c376d454b425555b1b0bda36e99f56ec307
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fb6a4c376d454b425555b1b0bda36e99f56ec307

Changed files:
  drivers/net/ethernet/hisilicon/hns3/hns3_enet.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=fb6a4c376d454b425555b1b0bda36e99f56ec307

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

The original Linux kernel CVE announcement for CVE-2026-45891 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45891

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: 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).