[CVE-2026-72402][MODERATE REGULAR] bpf: Mask pseudo pointer values in verifier logs [ Upstream

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

CVE: CVE-2026-72402
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: bpf: Mask pseudo pointer values in verifier logs [ Upstream
Commit: 1c53d16b174dd9e02243fc0e85089e2aa6a0d21a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1c53d16b174dd9e02243fc0e85089e2aa6a0d21a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72402
Analysis date: Sun, 16 Aug 2026 05:33:54 -0400
ActionableScore: 4
ActionableScore lower bound: 1
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
BPF verifier logs could expose kernel pointer values for pseudo pointer sources that were not included in the existing masking logic, allowing a local BPF-capable actor to obtain kernel addresses and weaken KASLR.

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

The original Linux kernel CVE announcement for CVE-2026-72402 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72402

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-2026-72402	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N';*CWE-200;CWE-532;CWE-209;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '5.5';DESCR 'BPF verifier logging could expose kernel pointer values because print_bpf_insn masked only some pointer bearing pseudo sources when pointer leaks were not allowed. BPF_PSEUDO_MAP_IDX, BPF_PSEUDO_MAP_IDX_VALUE, and BPF_PSEUDO_BTF_ID can also be resolved to kernel pointer values before the instruction is printed, so a local actor able to load a BPF program and read the verifier log may learn kernel addresses. For the CVSS the PR:L is used because triggering requires a local process with access to the BPF loading and verifier log interface, even if the system allows unprivileged BPF in some configurations. The issue is not network reachable and does not provide a write primitive or direct privilege escalation by itself. Impact is information disclosure, mainly kernel pointer exposure that can weaken KASLR and may assist exploitation of a separate kernel memory corruption bug. YES REQUIRES MANUAL CHECK.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3)	YES	BPF SIMPLEFIX LEAK LINUS  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=4
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended**::

## 2. Signal breakdown

Conservative signals:

* Confidentiality impact plausible: +1. The verifier log may expose kernel pointer values when pointer leaks are supposed to be masked.
* Broad/default/common subsystem: +1. BPF is a major kernel subsystem, but practical access is commonly privilege gated.
* Requires admin/root/CAP_* in typical deployments: -2. In the evaluated configuration, unprivileged BPF is disabled and BPF loading/log access normally requires CAP_BPF, CAP_SYS_ADMIN, root, or root-controlled sysctl policy.

Conservative total: 1.

Paranoid signals:

* Local unprivileged trigger: +1. Applies only in configurations where unprivileged BPF loading and verifier logs are available.
* Local unprivileged high-control kernel data-plane API refinement: +1. Applies only if unprivileged BPF is enabled, because BPF gives fine-grained control over verifier inputs.
* Confidentiality impact plausible: +1. Kernel pointer disclosure can weaken KASLR and support exploitation of a separate kernel bug.
* Broad/default/common subsystem: +1. BPF is widely deployed and security sensitive.

Paranoid total: 4.

Not applied:

* No generic memory corruption. The patch only extends masking of pointer-like immediates in log output.
* No direct privilege escalation. The leaked value is an address disclosure primitive, not a write or control-flow primitive.
* No reliable kernel crash or DoS.
* No network reachability.

## 3. Reachability analysis

The bug is reachable by an actor who can load or validate BPF programs and read verifier logs. In typical hardened or enterprise configurations, this is not available to ordinary local users because unprivileged BPF is disabled or BPF operations require CAP_BPF, CAP_SYS_ADMIN, CAP_NET_ADMIN, or root-controlled policy. If unprivileged BPF is enabled, a local user may be able to trigger the leak through crafted BPF instructions using pseudo pointer sources such as BPF_PSEUDO_MAP_IDX, BPF_PSEUDO_MAP_IDX_VALUE, or BPF_PSEUDO_BTF_ID. The issue is not remotely reachable by packet input alone.

Call-site confidence: high. The changed function and affected log masking logic are directly visible in the patch.

## 4. Severity interpretation

This behaves like an information disclosure issue, not memory corruption. Realistic impact is kernel pointer exposure in verifier logs, mainly weakening KASLR and helping a separate exploit chain. In privileged-only BPF configurations it is ordinary Low/Moderate-like. In unprivileged BPF configurations it becomes a borderline actionable Moderate candidate because kernel address disclosure from BPF has practical exploit-chain value.

## 5. One-sentence report phrase

BPF verifier logs could expose kernel pointer values for pseudo pointer sources that were not included in the existing masking logic, allowing a local BPF-capable actor to obtain kernel addresses and weaken KASLR.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended mainly to confirm the target product configuration for unprivileged BPF and verifier log access. If BPF is privileged-only, this can likely be treated as low priority. If unprivileged BPF is enabled, it should not be auto-closed because the leak may assist exploitation of other kernel memory corruption bugs.

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

Patch: bpf: Mask pseudo pointer values in verifier logs [ Upstream
Commit: 1c53d16b174dd9e02243fc0e85089e2aa6a0d21a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1c53d16b174dd9e02243fc0e85089e2aa6a0d21a

Changed files:
  kernel/bpf/disasm.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=1c53d16b174dd9e02243fc0e85089e2aa6a0d21a

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

The original Linux kernel CVE announcement for CVE-2026-72402 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72402

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:L/UI:N/S:U/C:L/I:N/A:N
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
  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: 1
  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).