[CVE-2026-45970][MODERATE 7.0] bonding: alb: fix UAF in rlb_arp_recv during bond up/down [ Upstream

[CVE-2026-45970][MODERATE 7.0] bonding: alb: fix UAF in rlb_arp_recv during bond up/down [ Upstream

[AL-KERNEL]

CVE: CVE-2026-45970
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: bonding: alb: fix UAF in rlb_arp_recv during bond up/down [ Upstream
Commit: fd54ddc929be1d6c3b3b7b35d6d4642a5d9e803c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fd54ddc929be1d6c3b3b7b35d6d4642a5d9e803c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45970
Analysis date: Wed, 27 May 2026 18:53:35 -0400
ActionableScore: 6
ActionableScore lower bound: 4
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-2026-45970 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45970

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-2026-45970	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-416;CWE-362;CWE-667;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'Bonding ALB can race RX processing against bond teardown, allowing rlb_arp_recv() to run while rx_hashtbl or related RLB state has already been freed. A local actor that can repeatedly bring the bond interface up and down can combine this with incoming ARP traffic and trigger a use after free in the receive path. For the CVSS the PR:L is used in the paranoid score because CAP_NET_ADMIN may be delegated to containers or reduced privilege network operators, although typical host control of bond up down is administrative. The issue is not purely network reachable because remote ARP traffic alone does not control bond teardown. Impact is at least denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) 	MAYBE	OOB NULLPTR RACE UAF NETWORK KERNEL_PANIC_PLUS_UAF HARDWARE DEBUGFS KPANIC 	-	-	checked

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

ActionableScore=6
ActionableScoreLower=4

1. ActionableScore
* Conservative score: 4
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate at minimum**::

2. Signal breakdown
* Generic memory corruption, strong primitive: +2. The patch and changelog identify the root cause as a UAF in `rlb_arp_recv()`.
* Real lifetime corruption: +1. RX handlers can access ALB/RLB state after `rlb_deinitialize()` frees `rx_hashtbl`.
* Reliable kernel crash / strong DoS: +1. KASAN/Oops shows crash in RX path during the race.
* Local privilege or delegated network admin: +1 in paranoid view. `CAP_NET_ADMIN` may be delegated to containers or reduced-privilege network operators.
* Network RX involvement: +1. ARP traffic participates in triggering the RX handler, but does not alone trigger teardown.
* Requires admin/CAP_NET_ADMIN in typical deployments: -2 conservative. Repeated `ip link set bond0 up/down` normally requires network administration privilege.
* Hard race / special timing: -1. Requires bond teardown racing with in-flight RX/ARP processing.

3. Reachability analysis
A reliable trigger requires local or delegated control over bond interface state plus incoming ARP traffic. A remote L2 peer can contribute ARP frames, but cannot normally force bond up/down cycles by itself. Containers matter if they receive `CAP_NET_ADMIN` or control over a bond device. This is not a pure remote networking vulnerability, but it is in a network RX path and fixes a real UAF.

4. Severity interpretation
This is more serious than ordinary Moderate because it is explicit memory lifetime corruption in a receive path. Conservative treatment is borderline due to `CAP_NET_ADMIN` and timing requirements. Paranoid treatment is Actionable Moderate because delegated network administration is common enough, and UAF in RX handling can be underestimated even without a demonstrated controlled reclaim primitive.

5. One-sentence report phrase
Bonding ALB teardown can free RLB state while `rlb_arp_recv()` is still processing ARP traffic, causing a use-after-free crash during bond up/down races.

6. Manual review recommendation
MANUAL CHECK REQUIRED. The bug is an explicit UAF in a network RX path, although practical exploitation likely requires local or delegated `CAP_NET_ADMIN` plus ARP traffic and race timing.

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

Patch: bonding: alb: fix UAF in rlb_arp_recv during bond up/down [ Upstream
Commit: fd54ddc929be1d6c3b3b7b35d6d4642a5d9e803c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fd54ddc929be1d6c3b3b7b35d6d4642a5d9e803c

Changed files:
  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=fd54ddc929be1d6c3b3b7b35d6d4642a5d9e803c

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

The original Linux kernel CVE announcement for CVE-2026-45970 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45970

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: 4
  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).