[CVE-2026-53106][LOW] bpf: Do not allow deleting local storage in NMI [ Upstream

[CVE-2026-53106][LOW] bpf: Do not allow deleting local storage in NMI [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53106
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: bpf: Do not allow deleting local storage in NMI [ Upstream
Commit: e84acaf936970b5b0be2c93bbf255295ba9406df
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e84acaf936970b5b0be2c93bbf255295ba9406df
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53106
Analysis date: Wed, 24 Jun 2026 15:53:18 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
BPF local storage deletion from NMI context can deadlock deferred RCU-based freeing paths, allowing a local privileged or delegated BPF user to cause a kernel hang or DoS, with no evidence of memory corruption or privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-53106 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53106

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: NO

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-2026-53106	LOW	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:N/I:N/A:H';*CWE-833;CWE-667;**CWE-400;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'BPF local storage deletion can deadlock when bpf_selem_unlink is reached from NMI context and the free path is deferred through kfree_rcu, call_rcu, or call_rcu_tasks_trace. A local attacker who can load or run suitable BPF tracing programs may trigger a kernel stall or hang by invoking storage delete helpers from an NMI reachable execution path. For the CVSS the PR:L is used for the paranoid score because delegated BPF or tracing capabilities may be available to a local service or reduced capability user without full host administrator privileges. The issue is not network reachable and requires local BPF execution capability. Impact is denial of service only because the patch indicates a deadlock condition and does not show a UAF, OOB access, information leak, or arbitrary write primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	DEADLOCK BPF SIMPLEFIX IMPROVEONLY LINUS 	NO	NO	checked

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

ActionableScore=2
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Conservative signals:

* Reliable kernel crash / strong DoS: +1. The commit describes a possible deadlock when BPF local storage deletion defers freeing through kfree_rcu(), call_rcu(), or call_rcu_tasks_trace() from NMI context.
* Hard or unreliable timing / special context required: -1. The vulnerable path requires reaching bpf_xxx_storage_delete() from NMI context, which the commit itself describes as an unlikely use case.
* Requires privileged BPF/tracing capability in typical deployments: -2. Loading or running the relevant BPF tracing programs normally requires CAP_BPF, CAP_PERFMON, CAP_SYS_ADMIN, or equivalent delegation.

Paranoid additional interpretation:

* Local BPF lifetime-control API concern: +1. BPF local storage helpers can affect kernel object lifetime and deferred free paths, so delegated BPF access deserves some additional triage sensitivity.
* Availability impact realistic: +1. If triggered, the deadlock can cause a kernel stall or hang rather than a harmless warning.

Not counted:

* No remote/network reachability.
* No generic memory corruption. The patch does not show UAF, OOB access, double free, type confusion, arbitrary write, or refcount takeover.
* No plausible privilege escalation signal. The described failure mode is deadlock/DoS only.
* No confidentiality or integrity impact.

## 3. Reachability analysis

The bug is reachable only by a local actor able to run suitable BPF tracing/local-storage-delete helper paths in an NMI-reachable context. In normal deployments this requires privileged BPF or tracing capabilities, not ordinary unprivileged local access. Namespaces or containers may reduce the practical privilege requirement if BPF or tracing capabilities are delegated to a service account or container root, which is why the paranoid score avoids treating it as fully host-root-only. The path is not network reachable and is not a default packet-processing exposure.

## 4. Severity interpretation

This behaves like an ordinary Moderate / Low-like local DoS issue. Theoretical impact is a kernel deadlock or stall through an unsafe NMI-context deferred-free path. Realistic exploitation evidence does not support memory corruption, information disclosure, integrity impact, or LPE. The issue should not be promoted to Important based on the supplied patch.

## 5. One-sentence report phrase

BPF local storage deletion from NMI context can deadlock deferred RCU-based freeing paths, allowing a local privileged or delegated BPF user to cause a kernel hang or DoS, with no evidence of memory corruption or privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED.

The issue is DoS-only, non-network-reachable, requires privileged or delegated BPF execution, and the patch does not indicate a concrete memory corruption or security-boundary bypass primitive.

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

Patch: bpf: Do not allow deleting local storage in NMI [ Upstream
Commit: e84acaf936970b5b0be2c93bbf255295ba9406df
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e84acaf936970b5b0be2c93bbf255295ba9406df

Changed files:
  kernel/bpf/bpf_local_storage.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=e84acaf936970b5b0be2c93bbf255295ba9406df

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

The original Linux kernel CVE announcement for CVE-2026-53106 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53106

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:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 0
  Paranoid ActionableScore: 2

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).