[CVE-2026-53096][MODERATE 7.0] bpf: Use RCU-safe iteration in dev_map_redirect_multi() SKB path [ Upstream

[CVE-2026-53096][MODERATE 7.0] bpf: Use RCU-safe iteration in dev_map_redirect_multi() SKB path [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53096
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: bpf: Use RCU-safe iteration in dev_map_redirect_multi() SKB path [ Upstream
Commit: 4a3d0fe30b907ff324b1b49756f7e713d67f3645
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4a3d0fe30b907ff324b1b49756f7e713d67f3645
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53096
Analysis date: Wed, 24 Jun 2026 14:18:17 -0400
ActionableScore: 5
ActionableScore lower bound: 2
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-2026-53096 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53096

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-2026-53096	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-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'An RCU iteration bug in the BPF DEVMAP_HASH redirect path can occur because dev_map_redirect_multi used hlist_for_each_entry_safe while concurrent map updates use RCU list primitives. On weakly ordered architectures such as ARM64 or POWER, the SKB redirect reader may observe a partially constructed or inconsistently published devmap entry and then dereference fields such as dst dev or dst dev ifindex. The realistic impact is a local denial of service through invalid pointer dereference or kernel crash during redirect processing. For the CVSS the PR:L paranoid value is used because some deployments delegate BPF and network administration capabilities to non root services or containers, even though typical unrestricted BPF and devmap setup requires elevated capabilities. The issue is not directly network reachable as packet traffic only exercises a BPF program and map configuration that must already exist locally. Impact is at least availability loss and in worst case may allow limited confidentiality or integrity impact due to RCU ordering and partially constructed kernel object exposure.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	WRITE KASAN OOB LOCK BPF SKB HARDWARE LINUS  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=5
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Weak or indirect corruption candidate: +1. The reader may observe a partially constructed RCU list node and dereference inconsistent object fields.
* Real lifetime or RCU corruption: +1. The bug is an RCU iteration mismatch between readers and concurrent RCU list writers.
* Reliable kernel crash or strong DoS: +1. Invalid dereference in the BPF redirect path can plausibly crash the kernel.
* Packet processing path: +1. The affected code is in the BPF devmap redirect path used by packet redirection.
* Hard race or architecture dependent timing: -1. The problematic behavior depends on concurrent update and redirect timing and is mainly relevant on weakly ordered architectures.
* Requires elevated capabilities in typical deployments: -2. Creating and updating BPF devmaps and configuring redirect paths usually requires CAP_BPF and CAP_NET_ADMIN or equivalent privileges.

Paranoid additions:

* Local lower privilege trigger interpretation: +1. Some deployments delegate BPF or network administration capabilities to containers, service accounts, or reduced capability root.
* Weak LPE concern: +1. A partially constructed kernel object can be observed and dereferenced, but no controlled reclaim, overwrite, callback, or type confusion primitive is shown.

## 3. Reachability analysis

This is not directly network reachable. Packets can exercise the redirect path, but an attacker must first have a suitable BPF devmap redirect setup and must race packet redirection against DEVMAP_HASH updates or deletions.

In typical host deployments this requires elevated privileges such as CAP_BPF and CAP_NET_ADMIN. In containerized or delegated networking environments, the practical privilege level may be lower if a tenant or service account can manage BPF maps and network redirect configuration.

The affected path is not default exposed to arbitrary local users, but BPF networking and devmap usage are realistic in high performance networking deployments. Exploitation is architecture and timing sensitive, especially on ARM64 or POWER.

## 4. Severity interpretation

This behaves above an ordinary Moderate only under the paranoid interpretation. The patch shows a real RCU correctness bug and possible observation of partially constructed nodes, but it does not show attacker controlled reclaim, arbitrary write, callback control, or a strong privilege escalation primitive.

Realistic impact is local kernel crash or DoS. Theoretical impact includes limited confidentiality or integrity concern due to inconsistent kernel object observation, but the evidence is not strong enough for an Important classification.

## 5. One sentence report phrase

An RCU unsafe iteration bug in the BPF DEVMAP_HASH SKB redirect path may allow a local actor with BPF and network administration capabilities, or delegated equivalents, to race map updates against packet redirection and trigger an invalid kernel object dereference leading primarily to DoS.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is an RCU race in a kernel BPF packet processing path with possible invalid dereference of partially published objects. It is not a proven LPE, but the combination of BPF, RCU lifetime semantics, and delegated capability deployments makes auto closure unsafe.

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

Patch: bpf: Use RCU-safe iteration in dev_map_redirect_multi() SKB path [ Upstream
Commit: 4a3d0fe30b907ff324b1b49756f7e713d67f3645
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4a3d0fe30b907ff324b1b49756f7e713d67f3645

Changed files:
  kernel/bpf/devmap.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=4a3d0fe30b907ff324b1b49756f7e713d67f3645

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

The original Linux kernel CVE announcement for CVE-2026-53096 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53096

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: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: 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).