[CVE-2026-64371][MODERATE 7.0] proc: protect ptrace_may_access() with exec_update_lock (part 1) [ Upstream

[CVE-2026-64371][MODERATE 7.0] proc: protect ptrace_may_access() with exec_update_lock (part 1) [ Upstream

[AL-KERNEL]

CVE: CVE-2026-64371
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: proc: protect ptrace_may_access() with exec_update_lock (part 1) [ Upstream
Commit: ae1e630bcaac739f625822078edbaea98366930d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ae1e630bcaac739f625822078edbaea98366930d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64371
Analysis date: Sat, 25 Jul 2026 11:07:05 -0400
ActionableScore: 6
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum**:: selected as Actionable Moderate at minimum, not auto-close.
Manual review required: YES

Summary:
A procfs authorization race allowed ptrace_may_access checks to run without exec_update_lock protection, potentially exposing protected process information during exec credential or dumpability transitions.

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

The original Linux kernel CVE announcement for CVE-2026-64371 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64371

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-2026-64371	MODERATE	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:N/A:N';CWE-362;CWE-367;*CWE-200;CWE-284;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '4.7';DESCR 'procfs access checks could race with exec because several paths called ptrace_may_access without holding exec_update_lock. A local user may be able to read procfs information while the target task is crossing an exec credential or dumpability transition, causing an access control bypass and information disclosure. For the CVSS the PR:L is used because reliable triggering requires a local user or local process that can access procfs and race the target task. The issue is not network reachable and is triggered through local procfs reads rather than packet traffic. Impact is primarily confidentiality loss. No memory corruption primitive is indicated by the changed code, so integrity and availability are not raised in the base score. For the paranoid score, choose the highest still defensible interpretation supported by the bug class and patch context, with preference for manual-review sensitivity over autoclosed false negatives.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)	YES	READ DISK LEAK LINUS  KPANIC INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK	NO	NO	checked

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

ActionableScore=6
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 6
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: selected as Actionable Moderate at minimum, not auto-close.

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local user can access procfs paths and attempt to race a target task during exec.
* Security-boundary bypass with practical sensitive-object access: +2. The bug is in ptrace_may_access based procfs authorization and can bypass intended procfs visibility rules across exec credential or dumpability transitions.
* Confidentiality impact plausible: +1. Exposed data may include proc task state, map_files information, namespace links, wchan, or stat fields.
* Broad/default/common subsystem: +1. procfs is a default and widely used kernel interface.
* Hard or unreliable race / special timing required: -1. Reliable triggering requires hitting an exec_update_lock race window.

Paranoid additional signal:

* Sensitive procfs task-state exposure: +2. In the higher-bound interpretation, map_files and namespace/proc task state exposure can reveal sensitive process layout or privileged process state. This raises triage priority without assuming memory corruption or LPE.

Not counted:

* No generic memory corruption. The patch does not show UAF, OOB access, arbitrary write, refcount takeover, or type confusion.
* No privilege escalation bonus. The issue is an access-control and information-disclosure race, not a demonstrated LPE primitive.
* No remote/network bonus. Triggering is via local procfs reads.

## 3. Reachability analysis

The bug is locally reachable through procfs operations such as stat, wchan, map_files, and namespace symlink reads. A normal local user may be able to attempt the race against a target process during exec, especially around credential or dumpability changes. Containers and namespaces can matter because procfs visibility and ptrace checks are often used as isolation boundaries, but this does not become a network-reachable issue. The affected paths are common and default-enabled, while practical exploitation depends on winning a timing window during exec.

## 4. Severity interpretation

This behaves more like an actionable Moderate than an ordinary Moderate because it affects a core security authorization path and can bypass procfs information-hiding rules. The realistic impact is confidentiality exposure, not kernel memory corruption or direct privilege escalation. The paranoid score is justified for manual triage because procfs access-control races around exec have historically produced subtle security-boundary bypasses, but the patch does not support treating it as a strong Important memory-corruption issue.

## 5. One-sentence report phrase

A procfs authorization race allowed ptrace_may_access checks to run without exec_update_lock protection, potentially exposing protected process information during exec credential or dumpability transitions.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED.

Reason: this is a security-boundary race in procfs ptrace-style access checks, with plausible sensitive information exposure across exec transitions, even though no memory corruption or direct LPE primitive is shown.

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

Patch: proc: protect ptrace_may_access() with exec_update_lock (part 1) [ Upstream
Commit: ae1e630bcaac739f625822078edbaea98366930d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ae1e630bcaac739f625822078edbaea98366930d

Changed files:
  fs/proc/array.c
  fs/proc/base.c
  fs/proc/namespaces.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=ae1e630bcaac739f625822078edbaea98366930d

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

The original Linux kernel CVE announcement for CVE-2026-64371 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64371

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:L/UI:N/S:U/C:L/I:N/A:N
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
  The Best / paranoid CVSS score: 4.7

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: 4
  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).