[CVE-2026-52975][MODERATE REGULAR] bonding: 3ad: implement proper RCU rules for port->aggregator [ Upstream

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

CVE: CVE-2026-52975
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: bonding: 3ad: implement proper RCU rules for port->aggregator [ Upstream
Commit: ba2272be04f0cb1e74e1e355ff32ef95df280731
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ba2272be04f0cb1e74e1e355ff32ef95df280731
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52975
Analysis date: Wed, 24 Jun 2026 13:06:29 -0400
ActionableScore: 4
ActionableScore lower bound: 2
Actionable bucket: Borderline, manual review recommended / Actionable Moderate watchlist
Manual review required: YES

Summary:
A data race in bonding 802.3ad `port->aggregator` handling can expose rtnetlink and status readers to inconsistent or stale aggregator pointers during concurrent state-machine updates, with realistic impact limited to local DoS and paranoid concern for RCU lifetime misuse.

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

The original Linux kernel CVE announcement for CVE-2026-52975 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52975

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 REGULAR
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-2026-52975	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:L/I:L/A:H';CWE-362;CWE-667;*CWE-416;*CWE-416;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A race in bonding 802.3ad handling can occur because port aggregator was accessed without proper RCU rules while the 3ad state machine updates the pointer and netlink or status paths read it concurrently. This can expose readers to an inconsistent or stale aggregator pointer and may lead to a NULL-pointer dereference or use-after-free style read in kernel context. For the CVSS the PR:L is used because reliable triggering normally requires a local process with network administration capability or control over a bonding interface, but this may be available to container root or delegated network management services rather than full host root. The issue is not directly network reachable through packet traffic alone. Impact is at least local denial of service via kernel crash, and in the paranoid interpretation may allow limited confidentiality or integrity impact due to an RCU stale pointer condition that should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended / Actionable Moderate watchlist (with actual score 3)	YES	WRITE KASAN OOB LOCK INIT NETWORK LOG HARDWARE LINUS SYZBOT  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=4
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: **2**
* Paranoid score: **4**
* Final recommended bucket: **Borderline, manual review recommended / Actionable Moderate watchlist**

## 2. Signal breakdown

**Conservative signals:**

* **Real lifetime corruption / RCU lifetime issue: +1**
  `port->aggregator` is a shared pointer updated by the 802.3ad state machine and read from rtnetlink/status paths without proper RCU access rules.

* **Weak / indirect corruption candidate: +1**
  The patch fixes unsafe concurrent pointer access, but the evidence is a KCSAN data race. There is no demonstrated attacker-controlled reclaim, overwrite, callback dispatch, or type confusion.

* **Hard or unreliable race / timing required: -1**
  The issue depends on concurrent bonding state-machine updates and userspace rtnetlink/status queries.

* **Requires CAP_NET_ADMIN in typical deployments: -1**
  Reliable triggering usually requires control over a bonding interface or network configuration. This is often CAP_NET_ADMIN, but not necessarily full host root because containers or delegated network namespaces may reduce the practical privilege bar.

* **Broad networking subsystem exposure: +1**
  Bonding is a standard Linux networking driver, but 802.3ad bonding is not a default path on most systems.

**Paranoid additional interpretation:**

* **Reliable kernel crash / strong DoS concern: +1**
  Several readers dereference `aggregator` fields after racing with updates. A NULL or stale pointer dereference is plausible, even though the report shows KCSAN rather than a concrete crash.

* **Availability impact realistic: +1**
  If the race manifests as an invalid dereference, the likely impact is a local kernel crash or networking subsystem disruption.

No remote/network-triggerable score is added. No strong LPE score is added. No strong memory corruption score is added because the patch does not show attacker-controlled reclaim, write-after-free, arbitrary write, type confusion, or callback control.

## 3. Reachability analysis

The likely trigger is local control-plane activity through rtnetlink, bonding configuration, or status queries racing with the 802.3ad state machine. In ordinary host deployments this usually requires CAP_NET_ADMIN or equivalent control over a bond device. In containerized or namespace-enabled environments, CAP_NET_ADMIN may be delegated to a reduced-privilege root or service account, so PR should not automatically be treated as full host-root. The issue is not directly reachable from packet traffic alone and requires an existing or creatable 802.3ad bonding setup.

## 4. Severity interpretation

This behaves more like a **borderline / actionable Moderate** than a clear Important-class vulnerability. The theoretical concern is stale pointer or UAF-style RCU misuse, but the demonstrated evidence is a KCSAN data race and the patch mainly enforces proper RCU read/write rules. Realistic impact is most defensibly local DoS. Privilege escalation is not strongly supported by the patch because there is no reclaim, overwrite, callback, refcount takeover, or controlled object confusion primitive.

## 5. One-sentence report phrase

A data race in bonding 802.3ad `port->aggregator` handling can expose rtnetlink and status readers to inconsistent or stale aggregator pointers during concurrent state-machine updates, with realistic impact limited to local DoS and paranoid concern for RCU lifetime misuse.

## 6. Manual review recommendation

**MANUAL CHECK REQUIRED**

Reason: this is an RCU race on a shared kernel pointer in a networking driver, with plausible stale pointer dereference behavior. It should not be auto-closed, but current evidence supports Actionable Moderate watchlist handling rather than a strong Important classification.

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

Patch: bonding: 3ad: implement proper RCU rules for port->aggregator [ Upstream
Commit: ba2272be04f0cb1e74e1e355ff32ef95df280731
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ba2272be04f0cb1e74e1e355ff32ef95df280731

Changed files:
  drivers/net/bonding/bond_3ad.c
  kernel/workqueue.c
  kernel/kthread.c
  arch/x86/kernel/process.c
  arch/x86/entry/entry_64.S
  drivers/net/bonding/bond_netlink.c
  net/core/rtnetlink.c
  net/core/dev.c
  net/netlink/af_netlink.c
  net/socket.c
  arch/x86/include/generated/asm/syscalls_64.h
  arch/x86/entry/syscall_64.c
  drivers/net/bonding/bond_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=ba2272be04f0cb1e74e1e355ff32ef95df280731

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

The original Linux kernel CVE announcement for CVE-2026-52975 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52975

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:L/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:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

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: 2
  Paranoid ActionableScore: 4

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 REGULAR

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).