[CVE-2026-90327][MODERATE REGULAR] phonet: pep: do not write beyond optlen in getsockopt [ Upstream

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

CVE: CVE-2026-90327
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: phonet: pep: do not write beyond optlen in getsockopt [ Upstream
Commit: 6054fed6bad08b6d03973e8ffca7f0c9394d1c30
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6054fed6bad08b6d03973e8ffca7f0c9394d1c30
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90327
Analysis date: Thu, 17 Sep 2026 16:42:48 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-90327 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90327

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: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-90327	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-90327 CHECK WITH IMPACT FROM ORIG NN MODERATE	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:L/A:L';*CWE-787;CWE-805;CWE-130;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N';BEST CVSS score: '4.4';DESCR 'pep_getsockopt can write one to three bytes beyond the caller supplied logical buffer because the reported length is clamped to optlen while put_user still stores a full integer. The overwrite affects userspace memory belonging to the calling process and does not directly corrupt kernel memory. For the CVSS the PR:L value is used because a local user or process must create or access a Phonet PEP socket and invoke getsockopt with a short optlen. The issue is not directly network reachable because the vulnerable operation is a local syscall rather than packet processing. Impact is primarily limited integrity loss in the calling application and possibly an application crash. No direct kernel privilege escalation primitive is established by the affected code.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)  SKIP CVE-2026-90327 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	DANGER SIMPLEFIX  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS	-	-	checked

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

ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Local unprivileged trigger. A process holding a Phonet PEP socket can invoke `getsockopt()` with an `optlen` smaller than `sizeof(int)`.
* No kernel-corruption point. The four-byte `put_user()` writes only to a user-supplied userspace address that is validated as writable.
* No reliable kernel crash point. The demonstrated effect is limited to one to three bytes beyond the caller-declared userspace buffer.
* No integrity point. Unauthorized modification of another principal, protected kernel state, or privileged application state is not established.
* No confidentiality point. No data is disclosed outside the calling process.
* No remote-reachability point. The vulnerable operation is a local syscall, not Phonet packet processing.
* No UAF, refcount mutation, controlled reclaim, arbitrary kernel write, authorization bypass, or privilege-escalation primitive is established.
* The previous LLM manual-check recommendation is not supported by an unresolved kernel-security primitive.

3. Reachability analysis

The direct trigger is a local process invoking `getsockopt()` on a Phonet PEP socket while supplying a short output length. The caller controls both the destination pointer and the length, and the resulting overwrite remains in that caller's writable userspace memory.

No host-admin-equivalent operation is needed for the vulnerable `getsockopt()` call itself. No namespace capability or prior privileged setup is shown as part of the relevant operation. The issue is deterministic and does not require a race, special timing, or remote traffic. Kernel support for Phonet and access to a suitable socket are prerequisites, but subsystem specialization alone does not justify a score reduction.

4. Primitive and severity interpretation

The exact primitive is a bounded one-to-three-byte overwrite beyond a caller-declared userspace buffer. It is not a kernel-buffer OOB write because `put_user()` targets userspace and verifies that the complete integer destination is writable.

The demonstrated consequence is corruption of adjacent memory in the calling process, potentially causing that process to malfunction or terminate. A security effect involving a privileged application would require an additional, unestablished interface through which an attacker could control that application's buffer placement and `optlen`.

This is therefore CLASS_C rather than CLASS_A or CLASS_B. There is no real UAF, kernel lifetime violation, kernel memory corruption, or security-boundary bypass. ImportantCandidate is NO and AutoDowngradeAllowed is YES because no unresolved kernel exploitation primitive remains.

5. One-sentence report phrase

`pep_getsockopt()` could write one to three bytes beyond a caller-declared userspace buffer, but the overwrite remains within caller-writable userspace and does not establish kernel corruption, privilege escalation, or remote reachability.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The issue is a tightly bounded self-directed userspace overwrite with no demonstrated kernel-security or cross-principal consequence.

7. Call-site confidence

Call-site confidence: medium

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

Patch: phonet: pep: do not write beyond optlen in getsockopt [ Upstream
Commit: 6054fed6bad08b6d03973e8ffca7f0c9394d1c30
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6054fed6bad08b6d03973e8ffca7f0c9394d1c30

Changed files:
  net/phonet/pep.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=6054fed6bad08b6d03973e8ffca7f0c9394d1c30

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

The original Linux kernel CVE announcement for CVE-2026-90327 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90327

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:N/I:L/A:N
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
  The Best / paranoid CVSS score: 4.4

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: unknown
  Paranoid ActionableScore: 1

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).