[CVE-2026-53084][MODERATE REGULAR] bpf: return VMA snapshot from task_vma iterator [ Upstream

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

CVE: CVE-2026-53084
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: bpf: return VMA snapshot from task_vma iterator [ Upstream
Commit: 83b8802c034e843b83a3e1ef6f30cdd4e9ec291c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=83b8802c034e843b83a3e1ef6f30cdd4e9ec291c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53084
Analysis date: Wed, 24 Jun 2026 14:40:28 -0400
ActionableScore: 4
ActionableScore lower bound: 2
Actionable bucket: Borderline manual review recommended
Manual review required: YES

Summary:
The BPF task_vma iterator could hold a per VMA lock while executing a BPF program, allowing helper induced lock ordering to deadlock the kernel path and cause local denial of service, typically requiring privileged BPF access but potentially lower privilege in delegated BPF environments.

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

The original Linux kernel CVE announcement for CVE-2026-53084 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53084

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-53084	MODERATE	CHECK	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-667;*CWE-833;**CWE-400;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'The BPF task_vma iterator could hold a per VMA lock while the BPF program body was executing. If the program calls helpers that acquire locks depending on mmap_lock, the lock order can become vm_lock to i_rwsem to mmap_lock to vm_lock and may deadlock the kernel path. For the CVSS the PR:L is used in the paranoid score because some environments delegate BPF capability or BPF program execution to non root service accounts or containerized users, even though many default systems restrict this to administrators. The issue is local only and is not network reachable. Impact is denial of service due to a deadlock or system stall. There is no strong evidence of a direct information disclosure or privilege escalation primitive because the fix primarily removes lock nesting and adds safe lifetime handling for vm_file in the returned snapshot.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended (with actual score 3)	YES	READ DEADLOCK BPF LINUS 	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=4
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 4
* Final recommended bucket: **Borderline manual review recommended**::

## 2. Signal breakdown

Conservative signals:

* Reliable kernel crash / strong DoS: +1. The patch fixes a lock ordering problem that can deadlock the kernel path through vm_lock -> i_rwsem -> mmap_lock -> vm_lock.
* Broad/common subsystem exposure: +1. BPF is a broadly deployed kernel subsystem, although this specific task_vma iterator path is not a general default unprivileged interface.
* Requires admin/root/CAP_BPF/CAP_SYS_ADMIN in typical deployments: -2. Loading or running this class of BPF iterator program is normally restricted to privileged users.

Conservative total: 2.

Paranoid additional signals:

* Local unprivileged or reduced privilege trigger: +1. Some environments delegate BPF capability or BPF program execution to service accounts, container roots, or reduced capability users.
* Local high control kernel API: +1. BPF gives userspace structured control over kernel execution paths and helper calls, which makes lock ordering bugs more actionable than ordinary admin only cleanup bugs.

Paranoid total: 4.

Not counted:

* No generic memory corruption bonus. The patch primarily fixes lock lifetime and lock ordering, not UAF, OOB write, double free, type confusion, or arbitrary write.
* No privilege escalation bonus. There is no demonstrated reclaim, stale object reuse, callback corruption, write primitive, or verifier bypass.
* No confidentiality or integrity bonus. The visible impact is deadlock or stall, not data exposure or modification.

## 3. Reachability analysis

The bug is local only and is not network reachable. A trigger requires execution of a BPF program using the task_vma iterator and helper behavior that introduces the problematic lock dependency. In default hardened deployments this normally requires CAP_BPF, CAP_SYS_ADMIN, or equivalent privilege, so the conservative interpretation treats it as privileged local DoS. In delegated BPF environments, containerized setups, or service models where non-root users can run selected BPF programs, the practical PR may be lower, which justifies the paranoid score.

## 4. Severity interpretation

This behaves more like a borderline actionable Moderate than an Important vulnerability. The realistic impact is denial of service through kernel deadlock or stall. The patch touches sensitive BPF and VMA lifetime handling, including vm_file refcounting for the returned snapshot, so manual review is reasonable. However, the evidence does not support treating it as memory corruption or privilege escalation.

## 5. One-sentence report phrase

The BPF task_vma iterator could hold a per VMA lock while executing a BPF program, allowing helper induced lock ordering to deadlock the kernel path and cause local denial of service, typically requiring privileged BPF access but potentially lower privilege in delegated BPF environments.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED.

Reason: BPF iterator locking and trusted pointer lifetime rules are security sensitive, but the patch supports DoS through lock ordering rather than a demonstrated memory corruption or privilege escalation primitive.

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

Patch: bpf: return VMA snapshot from task_vma iterator [ Upstream
Commit: 83b8802c034e843b83a3e1ef6f30cdd4e9ec291c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=83b8802c034e843b83a3e1ef6f30cdd4e9ec291c

Changed files:
  kernel/bpf/task_iter.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=83b8802c034e843b83a3e1ef6f30cdd4e9ec291c

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

The original Linux kernel CVE announcement for CVE-2026-53084 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53084

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:H
  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: 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).