[CVE-2026-80670][MODERATE REGULAR] perf tools: Use perf_env__get_cpu_topology() in machine__resolve() [ Upstream

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

CVE: CVE-2026-80670
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: perf tools: Use perf_env__get_cpu_topology() in machine__resolve() [ Upstream
Commit: b9e8406651dcc1c19238aad11861a758683525b4
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b9e8406651dcc1c19238aad11861a758683525b4
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80670
Analysis date: Fri, 28 Aug 2026 05:57:01 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A crafted perf.data file can trigger an out-of-bounds heap read in perf tools because machine__resolve uses an untrusted CPU index without validating it against env nr_cpus_avail, causing limited information disclosure or a perf process crash during local file processing.

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

The original Linux kernel CVE announcement for CVE-2026-80670 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80670

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-80670	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:N/UI:R/S:U/C:L/I:N/A:L';CWE-125;*CWE-20;CWE-129;Other CVSS 'AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N';BEST CVSS score: '4.4';DESCR 'An out-of-bounds heap read in perf tools can occur because machine__resolve reads env cpu indexed by al cpu from an untrusted perf.data sample without validating the index against env nr_cpus_avail. A crafted perf.data file can provide a large CPU index and make perf read outside the allocated CPU topology array during local file processing. For the CVSS the PR:N is used because the attacker does not need an account on the victim system if they can supply a file that is later processed by perf. UI:R is used because a user or automated analysis workflow must open or process the crafted perf.data file. The issue is not network reachable by itself and affects the perf userspace tool rather than the running kernel. Impact is primarily limited confidentiality impact from an out-of-bounds heap read and possible low availability impact if the perf process crashes.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)  SKIP CVE-2026-80670 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	WRITE OOB SIMPLEFIX LOG HARDWARE  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS	-	-	checked

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

ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Triggered signals:

* Confidentiality impact plausible: +1
  The bug is an out-of-bounds heap read from a crafted perf.data file. The read value may influence reported CPU socket topology and could theoretically disclose limited process heap data.

Paranoid-only signal:

* Availability impact realistic: +1
  A sufficiently malformed index could plausibly crash the perf userspace process, but this is not a kernel crash and not system-wide DoS.

Not applied:

* Remote reachable: +0
  The issue is file-based and not network-triggerable by itself.

* Local unprivileged kernel trigger: +0
  This affects the perf userspace tool, not a kernel syscall or kernel runtime path.

* Generic memory corruption: +0
  This is a read-only OOB access, with no write primitive, UAF, double-free, or object lifetime corruption.

* Privilege escalation plausible: +0
  No kernel memory corruption, arbitrary write, controlled object reuse, or privilege boundary bypass is shown.

* Reliable kernel crash / strong DoS: +0
  The worst realistic availability impact is a perf process crash, not kernel panic.

## 3. Reachability analysis

The attacker needs to provide a crafted perf.data file that is later opened or processed by perf. No local account is required if the attacker can deliver the file to a user or automated analysis workflow, but user interaction or workflow processing is required. Namespaces and containers do not materially increase severity because the vulnerable code is in the perf userspace tool. The affected path is reachable when perf parses untrusted samples containing a crafted CPU index. This is not a default network-exposed service and does not affect the running kernel directly.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like userspace parser issue, not an Important kernel vulnerability. The demonstrated primitive is an out-of-bounds heap read with limited confidentiality concern and possible perf process crash. There is no evidence of kernel memory corruption, LPE, persistent system impact, or direct remote attack surface.

## 5. One-sentence report phrase

A crafted perf.data file can trigger an out-of-bounds heap read in perf tools because machine__resolve uses an untrusted CPU index without validating it against env nr_cpus_avail, causing limited information disclosure or a perf process crash during local file processing.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: this is an OOB read from attacker-controlled input, so it should not be ignored automatically, but the issue is limited to a userspace perf parser path and does not show kernel memory corruption or privilege escalation.

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

Patch: perf tools: Use perf_env__get_cpu_topology() in machine__resolve() [ Upstream
Commit: b9e8406651dcc1c19238aad11861a758683525b4
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b9e8406651dcc1c19238aad11861a758683525b4

Changed files:
  tools/perf/util/event.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=b9e8406651dcc1c19238aad11861a758683525b4

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

The original Linux kernel CVE announcement for CVE-2026-80670 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80670

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:N/UI:R/S:U/C:L/I:N/A:N
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/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: 1
  Paranoid ActionableScore: 2

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).