[CVE-2026-64553][MODERATE REGULAR] net: psample: fix info leak in PSAMPLE_ATTR_DATA [ Upstream

[CVE-2026-64553][MODERATE REGULAR] net: psample: fix info leak in PSAMPLE_ATTR_DATA [ Upstream

[AL-KERNEL]

CVE: CVE-2026-64553
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net: psample: fix info leak in PSAMPLE_ATTR_DATA [ Upstream
Commit: 0d3ea2ccddda442077fc44f11d873209c97ec50b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0d3ea2ccddda442077fc44f11d873209c97ec50b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64553
Analysis date: Wed, 29 Jul 2026 01:38:14 -0400
ActionableScore: 3
ActionableScore lower bound: 1
Actionable bucket: Borderline manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-64553 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64553

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.

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

CVE-2026-64553	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-908;CWE-665;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '5.5';DESCR 'PSAMPLE_ATTR_DATA can disclose uninitialized kernel bytes because psample open coded netlink attribute construction and did not clear the 4 byte alignment padding when data_len is not divisible by 4. A local receiver of psample generic netlink events may observe up to 3 bytes of stale kernel memory per sampled packet, and repeated sampling can increase exposure even though the leak is small and not a memory corruption primitive. For the CVSS the PR:L is used for the paranoid score because a local process with access to psample events may read the leaked padding, while creating or changing packet sampling rules usually requires CAP_NET_ADMIN. The issue is not directly network reachable because the leak is delivered through local generic netlink messages, although network traffic may be the sampled input if psample is already configured. Impact is confidentiality disclosure only, with no integrity impact, availability impact, or privilege escalation primitive shown by the code path.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended (with actual score 2) 	MAYBE	SIMPLEFIX LEAK SKB PACKET  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=3
ActionableScoreLower=1

1. ActionableScore
* Conservative score: 1
* Paranoid score: 3
* Final recommended bucket: **Borderline manual review recommended**::

2. Signal breakdown
* Confidentiality impact plausible: +1. The patch fixes a concrete leak of uninitialized kernel padding bytes in PSAMPLE_ATTR_DATA.
* Local unprivileged trigger: +1 in the paranoid interpretation. A local psample listener may read leaked padding if psample events are already being generated.
* Rare or configuration dependent exposure: -1 conservative. psample packet sampling normally requires explicit configuration and is not a default data path for most systems.
* Requires admin or CAP_NET_ADMIN in typical deployments: -2 conservative. Creating or changing packet sampling rules usually requires administrative network privileges.
* No memory corruption score. The bug is an information disclosure through unzeroed netlink padding, not UAF, OOB write, double free, or object lifetime corruption.
* No LPE score. The patch does not show a write primitive, reclaim primitive, type confusion, callback control, or privilege escalation path.

3. Reachability analysis
The leak is delivered through local generic netlink psample messages. It is not directly network reachable, although network traffic may be the sampled input when psample is already configured. In typical deployments, configuring psample requires CAP_NET_ADMIN, but a local process that can subscribe to psample events may observe the leaked padding once sampling exists. Namespace behavior may lower practical barriers in delegated network namespaces, but the issue remains local rather than remote.

4. Severity interpretation
This behaves like a concrete but small kernel information leak, not an Important class memory corruption issue. The realistic impact is disclosure of up to 3 stale kernel bytes per sampled packet, potentially repeated over time. Theoretical sensitivity exists because repeated kernel byte leaks can assist other attacks, but the patch does not support integrity impact, availability impact, or privilege escalation by itself.

5. One-sentence report phrase
psample may leak uninitialized kernel padding bytes in PSAMPLE_ATTR_DATA netlink messages when sampled packet data length is not 4 byte aligned, allowing a local psample receiver to observe small stale kernel memory fragments.

6. Manual review recommendation
MANUAL CHECK REQUIRED.
Reason: this is a concrete kernel information leak with possible repeated exposure, even though it is local and configuration dependent.

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

Patch: net: psample: fix info leak in PSAMPLE_ATTR_DATA [ Upstream
Commit: 0d3ea2ccddda442077fc44f11d873209c97ec50b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0d3ea2ccddda442077fc44f11d873209c97ec50b

Changed files:
  net/psample/psample.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=0d3ea2ccddda442077fc44f11d873209c97ec50b

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

The original Linux kernel CVE announcement for CVE-2026-64553 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64553

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: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: 3

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).