[CVE-2026-80876][LOW] ring-buffer: Fix event length with forced 8-byte alignment [ Upstream

[CVE-2026-80876][LOW] ring-buffer: Fix event length with forced 8-byte alignment [ Upstream

[AL-KERNEL]

CVE: CVE-2026-80876
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: ring-buffer: Fix event length with forced 8-byte alignment [ Upstream
Commit: 7c9f0ccf9f04142458d2ac3d39414f4acae242f0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7c9f0ccf9f04142458d2ac3d39414f4acae242f0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80876
Analysis date: Fri, 04 Sep 2026 17:20:34 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: YES

Summary:
Incorrect ring-buffer event length accounting under forced 8-byte alignment can make small trace events report 4 extra bytes, potentially exposing minor trace-buffer padding or metadata to a local tracing reader, but it is not network reachable and does not show memory corruption, privilege escalation, or reliable DoS.

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

The original Linux kernel CVE announcement for CVE-2026-80876 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80876

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: LOW
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
======================================================================

CVE-2026-80876	LOW	https://www.kernelcve.org/list/?q=CVE-2026-80876 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:L/I:N/A:N';CWE-682;CWE-704;*CWE-200;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:N';BEST CVSS score: '3.3';DESCR 'ring buffer event length reporting can be incorrect on architectures using RB_FORCE_8BYTE_ALIGNMENT because the stored length field is not always subtracted for small events. A local tracing user may observe trace records with a data length that is 4 bytes larger than expected, which can corrupt trace interpretation and may expose a small amount of trace buffer metadata or padding in a conservative reading. For the CVSS the PR:L is used for the paranoid score because some systems may delegate tracefs or tracing access to non root local users, but normal tracing control is usually restricted. The issue is not network reachable. Impact is at most a low confidentiality concern for trace data and there is no evidence of memory corruption, privilege escalation, or system availability impact.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	TRACE HARDWARE LINUS 	NO	NO	checked

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

ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Conservative signals:

* Requires admin/root/CAP_* in typical deployments: -2. Access to ftrace/tracefs and ring-buffer tracing data is normally restricted to root or privileged tracing users.
* Rare AND difficult-to-reach subsystem/configuration: -1. The issue requires architectures/configurations where `RB_FORCE_8BYTE_ALIGNMENT` is true.
* No strong DoS signal. The patch describes incorrect length reporting and weird trace output, not panic, hang, UAF, OOB write, or reliable crash.
* No memory corruption signal. The changed code fixes length accounting, but does not show overwrite, stale pointer, UAF, double-free, refcount misuse, or object confusion.

Paranoid signals:

* Local unprivileged trigger: +1 only in deployments where tracefs access is delegated to non-root users.
* Confidentiality impact plausible: +1 only conservatively, because a local tracing reader may observe 4 extra bytes of trace-buffer metadata or padding.
* Rare configuration: -1 due to dependence on forced 8-byte alignment behavior.

Net paranoid score: 1.

## 3. Reachability analysis

The bug is local only and is reached through tracing/ring-buffer consumers, not through packet processing or any remote protocol. In normal deployments, tracing control and trace-buffer access require root or equivalent privileges, so the conservative score treats this as effectively non-actionable from an attacker perspective. Namespaces do not usually make tracefs safely available to unprivileged users, but some systems may delegate tracing access to service accounts or debugging users, which justifies the low paranoid score.

The affected path is not a broad default attack surface. It depends on `RB_FORCE_8BYTE_ALIGNMENT`, observed on riscv64 with relevant alignment configuration, and the demonstrated effect is malformed trace length reporting.

## 4. Severity interpretation

This behaves like a correctness bug or Low-like informational issue, not an Important-class vulnerability. The realistic impact is incorrect trace event length reporting. The only defensible security concern is a very small local confidentiality concern if extra trace-buffer padding or metadata becomes visible to a user who already has tracing read access. There is no evidence of privilege escalation, generic memory corruption, persistent corruption, or system-wide availability impact.

## 5. One-sentence report phrase

Incorrect ring-buffer event length accounting under forced 8-byte alignment can make small trace events report 4 extra bytes, potentially exposing minor trace-buffer padding or metadata to a local tracing reader, but it is not network reachable and does not show memory corruption, privilege escalation, or reliable DoS.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED. NO MANUAL CHECK REQUIRED COULD BE AUTOCLOSED.

Reason: the patch is a narrow accounting fix for trace event length calculation, with no demonstrated crash, memory corruption, privilege escalation primitive, or remotely reachable attack surface.

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

Patch: ring-buffer: Fix event length with forced 8-byte alignment [ Upstream
Commit: 7c9f0ccf9f04142458d2ac3d39414f4acae242f0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7c9f0ccf9f04142458d2ac3d39414f4acae242f0

Changed files:
  kernel/trace/ring_buffer.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=7c9f0ccf9f04142458d2ac3d39414f4acae242f0

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

The original Linux kernel CVE announcement for CVE-2026-80876 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80876

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:N
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
  The Best / paranoid CVSS score: 3.3

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: 0
  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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).