[CVE-2026-68301][LOW] net: hsr: fix memory leak on slave unregistration by removing synced VLANs [ Upstream

[CVE-2026-68301][LOW] net: hsr: fix memory leak on slave unregistration by removing synced VLANs [ Upstream

[AL-KERNEL]

CVE: CVE-2026-68301
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net: hsr: fix memory leak on slave unregistration by removing synced VLANs [ Upstream
Commit: f72c312af6c7897ab0f8a2b5a63f917a207a4143
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f72c312af6c7897ab0f8a2b5a63f917a207a4143
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68301
Analysis date: Mon, 10 Aug 2026 17:33:11 -0400
ActionableScore: 3
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like, not an Important candidate
Manual review required: YES

Summary:
HSR slave teardown fails to remove VLAN IDs synced from the master, leaving VLAN reference-counted objects allocated after slave unregistration and allowing sustained local resource-exhaustion DoS in configurations where an attacker can repeatedly create and destroy HSR setups.

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

The original Linux kernel CVE announcement for CVE-2026-68301 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68301

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: LOW
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
======================================================================

CVE-2026-68301	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'HSR slave unregistration can leak VLAN tracking objects because VLAN IDs synced from the HSR master to slave A or slave B are not removed before the slave is detached. The leaked references can keep vlan_info or vlan_vid_info allocations alive after the slave device is destroyed. This is a resource leak and refcount cleanup issue rather than a use after free or arbitrary memory corruption primitive. For the CVSS the PR:L is used for the paranoid score because a local user with delegated CAP_NET_ADMIN in a network namespace or a reduced capability container may be able to create and destroy HSR setups repeatedly. The issue is not directly network reachable and requires local or namespace level network control plane access. Impact is denial of service through sustained memory exhaustion, with no supported confidentiality or integrity impact.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like, not an Important candidate (with actual score 2)	YES	SIMPLEFIX LEAK NETWORK HARDWARE LINUS SYZBOT  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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

ActionableScore=3
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 3
* Final recommended bucket: **Ordinary Moderate / Low-like, not an Important candidate**::

## 2. Signal breakdown

Conservative signals:

* Refcount / lifetime cleanup bug: +1
  HSR fails to drop VLAN VID references synced to slave devices, leaving vlan_info / vlan_vid_info allocated after slave destruction.
* Availability impact possible: +1
  Repeated create / unregister cycles can accumulate leaked kernel memory and eventually cause resource exhaustion.
* Requires CAP_NET_ADMIN in typical deployments: -2
  Creating HSR devices, configuring VLAN propagation, and unregistering slave devices normally require network administration privileges.

Conservative total: 0.

Paranoid signals:

* Local namespace-level trigger: +1
  In environments with delegated CAP_NET_ADMIN, containers, or unprivileged user namespaces, a reduced-privilege actor may be able to create and destroy HSR setups.
* Refcount / lifetime cleanup bug: +1
  The leaked VLAN references survive device teardown.
* Cross-boundary resource impact: +1
  If reachable from a container or delegated network namespace, the leak consumes host kernel memory rather than only container-local memory.

Paranoid total: 3.

Not applied:

* No remote reachable signal. The bug is not triggered by packet reception alone.
* No generic memory corruption signal. The patch fixes a missing vlan_vids_del_by_dev() cleanup, not UAF, double free, OOB write, type confusion, or arbitrary write.
* No privilege escalation signal. There is no supported path to LPE.
* No confidentiality or integrity impact. The issue is a memory leak / resource retention bug.

## 3. Reachability analysis

The realistic trigger requires local network control-plane access: creating or operating an HSR master with slave devices, bringing it up so VLAN 0 is synced, and then unregistering or destroying the slave while HSR is active. In normal host deployments this requires CAP_NET_ADMIN, so the conservative interpretation is low priority.

Namespaces can lower the practical privilege requirement if an attacker is given CAP_NET_ADMIN inside a container or network namespace and can create HSR devices. In that model, repeated namespace cleanup or interface destruction could leak host kernel memory. The subsystem is not broadly default-exposed, and HSR is a specialized networking feature, but it is reachable through ordinary kernel network-device management paths when enabled.

Call-site confidence: high. The patch directly modifies hsr_del_port(), the teardown path described in the commit message.

## 4. Severity interpretation

This behaves like a resource leak / cleanup bug, not a memory corruption vulnerability. The practical impact is sustained local DoS through memory exhaustion after repeated operations. It should not be treated as Important unless additional evidence shows cross-namespace abuse at scale in a target product configuration.

The paranoid score is higher only because delegated CAP_NET_ADMIN can make the trigger available to a reduced-privilege container or namespace actor. Even then, the vulnerability class remains resource exhaustion only.

## 5. One-sentence report phrase

HSR slave teardown fails to remove VLAN IDs synced from the master, leaving VLAN reference-counted objects allocated after slave unregistration and allowing sustained local resource-exhaustion DoS in configurations where an attacker can repeatedly create and destroy HSR setups.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED.

NO MANUAL CHECK REQUIRED COULD BE AUTOCLOSED because this is a bounded resource leak / refcount cleanup issue with no evidence of UAF, OOB access, arbitrary write, privilege escalation, or direct network reachability.

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

Patch: net: hsr: fix memory leak on slave unregistration by removing synced VLANs [ Upstream
Commit: f72c312af6c7897ab0f8a2b5a63f917a207a4143
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f72c312af6c7897ab0f8a2b5a63f917a207a4143

Changed files:
  net/hsr/hsr_slave.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=f72c312af6c7897ab0f8a2b5a63f917a207a4143

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

The original Linux kernel CVE announcement for CVE-2026-68301 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68301

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:L/PR:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: 0
  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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).