[CVE-2026-93148][MODERATE 7.0] bpf: Reject MEM_ALLOC BTF accesses past object bounds [ Upstream

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

CVE: CVE-2026-93148
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: bpf: Reject MEM_ALLOC BTF accesses past object bounds [ Upstream
Commit: e626a50d07d43421cbf7bfb5a084b33a5e276b6e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e626a50d07d43421cbf7bfb5a084b33a5e276b6e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93148
Analysis date: Fri, 18 Sep 2026 08:52:43 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-93148 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93148

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-2026-93148	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-93148 CHECK WITH IMPACT FROM ORIG NN LOW	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-787;CWE-125;*CWE-20;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H';BEST CVSS score: '7';DESCR 'A BPF verifier bounds bug can allow MEM_ALLOC BTF typed objects to be accessed past their statically allocated object size when flexible array walking is incorrectly applied. A local attacker who can load a suitable BPF program may be able to create an out of bounds access through BTF struct walking, kfunc type checks, or kptr type checks. For the CVSS the PR:L is used in the paranoid score because some systems delegate BPF loading to low privileged local users or service accounts, even though many default deployments restrict these helpers to administrative capabilities. The issue is not network reachable and requires local code execution through the BPF loading path. Impact is at least local denial of service via kernel memory corruption and in worst case may allow confidentiality or integrity impact and privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6)	YES	BPF LOG IMPROVEONLY LINUS  KPANIC INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHERTHAN5 DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH	YES	NO	checked

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

ActionableScore=6
ActionableScoreLower=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 5
* Conservative score: 5. No floor or cap changed the score.
* Raw paranoid score: 6
* Paranoid score: 6. No floor or cap changed the score.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Conservative signals:

* +2 Strong corruption primitive. The verifier could allow MEM_ALLOC BTF typed object access past the statically allocated object size because flexible array relaxation was applied where the object allocation does not include trailing flexible storage.
* +1 Confidentiality plausible. A verifier bounds failure on BTF object access can plausibly permit out of bounds kernel object reads through BPF access paths, although no complete disclosure chain is supplied.
* +1 Integrity plausible. The same verifier bounds failure may permit out of bounds writes or invalid typed pointer acceptance in kptr or kfunc paths, making kernel memory integrity impact plausible.
* +1 Memory layout invariant restoration. The patch restores consistency between the static BTF object allocation size and the size accepted by BTF struct walking.

Paranoid additional signal:

* +1 Weak LPE concern. This is more than a generic BPF bug because the verifier may accept a pointer or typed access beyond the allocated MEM_ALLOC object, and the affected paths include BTF access, kfunc type checks, and kptr type checks. This creates unresolved exploitation leverage that requires manual review.

Non-awarded signals:

* RealUAF not awarded. The patch establishes an object bounds violation, not use after free.
* Controlled reclaim not demonstrated.
* Arbitrary kernel read or write not demonstrated as a complete primitive.
* Practical exploit chain not demonstrated.
* Local unprivileged trigger not awarded because the complete BPF load and execution privilege boundary is unresolved.
* Remote reachability not awarded.
* Strong LPE leverage +2 not awarded because no controlled reclaim, directed arbitrary write, credential overwrite, callback control, or demonstrated privilege escalation is supplied.
* Extra availability not awarded because no distinct crash or persistent availability mechanism is established beyond the corruption risk.
* Concrete repeated release or refcount signal not applicable.

3. Reachability analysis

The trigger requires loading or verifying a suitable BPF program that uses MEM_ALLOC BTF typed objects, such as objects created through bpf_obj_new, and reaches the affected BTF struct walk, kfunc, or kptr type checking paths.

Ordinary unprivileged reachability is not established. Modern deployments commonly restrict BPF loading through CAP_BPF, CAP_SYS_ADMIN, CAP_NET_ADMIN for some attach paths, sysctl policy, or LSM policy. The supplied patch does not resolve whether the full load, helper or kfunc availability, attach requirements, and execution path can be completed by an ordinary user.

HostAdminRequired is UNKNOWN rather than YES because the input does not positively prove that host root or host admin equivalent privilege is required in every evaluated deployment. It is also not NO because below host admin reachability is not positively established.

NamespaceScopedPrivilege is UNKNOWN. The patch involves BPF verifier and typed object logic, not just a namespace scoped network operation. No evidence shows that all required BPF loading, helper availability, attach, and execution steps are available inside attacker controlled namespaces.

No direct network trigger is established. No special hardware requirement is established. No race or timing requirement is established.

4. Primitive and severity interpretation

The exact primitive is a BPF verifier object bounds violation. Flexible array relaxation is valid for ordinary BTF walking, but MEM_ALLOC pointers refer to objects allocated with the static BTF type size. Allowing BTF struct walking past that size can accept out of bounds access or type matching past the allocated object.

This is not a UAF and not a repeated release or refcount bug. It is not cleanup only. The relevant operation happens in verifier access and type checking logic before unsafe BPF memory access is accepted.

PrimitiveClass is CLASS_A because the patch directly fixes a verifier bounds bypass that can permit access past kernel object allocation bounds. The demonstrated consequence is an unsafe accepted access beyond object bounds. The speculative consequence is privilege escalation through exploitation of the resulting OOB read or write capability, but that complete chain is not demonstrated.

ImportantCandidate is YES because BPF verifier bounds bugs can protect the main boundary between loaded BPF code and kernel memory safety, and this patch affects MEM_ALLOC object access plus kfunc and kptr type checks.

AutoDowngradeAllowed is NO because automatically closing this as ordinary Moderate would risk discarding a concrete kernel object bounds primitive with unresolved confidentiality, integrity, and privilege escalation implications.

Likely operational severity is Actionable Moderate at minimum, with Strong Important potential depending on actual BPF privilege exposure and whether the accepted out of bounds access is write capable in affected kernels.

5. One-sentence report phrase

A BPF verifier bounds bug can allow MEM_ALLOC BTF typed objects to be accessed past their static allocation size through flexible array relaxation, creating a plausible out of bounds kernel memory access primitive that requires manual review for confidentiality, integrity, and privilege escalation impact.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a BPF verifier object bounds bug with plausible OOB read or write impact, and the complete exploitability depends on BPF privilege exposure and the exact access capabilities accepted by the affected verifier paths.

7. Call-site confidence

Call-site confidence: medium

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

Patch: bpf: Reject MEM_ALLOC BTF accesses past object bounds [ Upstream
Commit: e626a50d07d43421cbf7bfb5a084b33a5e276b6e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e626a50d07d43421cbf7bfb5a084b33a5e276b6e

Changed files:
  include/linux/bpf.h
  kernel/bpf/btf.c
  kernel/bpf/verifier.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=e626a50d07d43421cbf7bfb5a084b33a5e276b6e

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

The original Linux kernel CVE announcement for CVE-2026-93148 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93148

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:H/I:H/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: 5
  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).