[CVE-2026-97533][MODERATE 7.0] x86/mm/pat: Acquire init_mm read lock on attribute changes to avoid UAF [ Upstream

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

CVE: CVE-2026-97533
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: x86/mm/pat: Acquire init_mm read lock on attribute changes to avoid UAF [ Upstream
Commit: e21a9ea81426a85fdb0cdcfcc99d5d9c16b402ab
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e21a9ea81426a85fdb0cdcfcc99d5d9c16b402ab
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97533
Analysis date: Sat, 26 Sep 2026 14:38:41 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-97533 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97533

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.

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

CVE-2026-97533	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-97533 CHECK WITH IMPACT FROM ORIG NN MODERATE	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:H/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A race between a lockless CPA page table walk and concurrent CPA collapse can free the page table that contains a previously obtained PTE. A later set_pte_atomic call can then write through the stale PTE pointer, resulting in a use after free write and possible corruption of reused kernel memory. Reliable triggering requires winning a timing window, therefore AC:H is appropriate. For the CVSS the PR:L value is used for the paranoid case because a local user may be able to trigger module autoload or another kernel operation that indirectly reaches the relevant CPA paths without full administrative control. The base case uses PR:H because direct control of module mapping and memory attribute changes is normally privileged. The issue is not directly network reachable. Impact is at least a local denial of service through memory corruption and a kernel crash. In the worst defensible case the stale PTE write may affect reused kernel data and could permit privilege escalation, so confidentiality and integrity impact require manual review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)  SKIP CVE-2026-97533 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	READ LOCK DEADLOCK INIT RACE UAF HARDWARE KPANIC MEMORY  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

ActionableScore=5
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 5
* Raw paranoid score: 3
* Paranoid score: 5
* Applied conservative REAL UAF FLOOR 5: 3 -> 5
* Applied paranoid REAL UAF FLOOR 5: 3 -> 5
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +2 Real UAF. CPA collapse can free the page-table page containing a PTE retained by the lockless attribute-change walker.
* +1 Constrained post-free kernel write. `set_pte_atomic()` writes through the stale PTE pointer. This is stronger than a read-only stale dereference, but the destination after reuse and written PTE value are not shown to be attacker-controlled.
* FLOOR 5 applies because the stale reference is used by an active page-table operation that writes into freed kernel storage. This is broader than an immediate cleanup fault and leaves meaningful corruption leverage unresolved.
* No race penalty. The patch establishes a race but does not establish that the timing is one-shot, exceptionally narrow, or impractical to repeat.
* No privilege penalty. Module mapping involvement is established, but the complete attacker-facing trigger and its privilege boundary are not.
* No reliable-crash point. A crash is plausible, but the supplied evidence directly establishes UAF corruption rather than a reliably reproducible panic.
* Controlled reclaim, replacement-object shaping, arbitrary write, disclosure, callback control, and demonstrated LPE are not established.
* No repeated release/refcount signal exists. There is no first release followed by a second lifetime mutation on the same reference.
* No confidentiality or integrity bonus is awarded merely because reused kernel memory could theoretically be affected.

3. Reachability analysis

The complete trigger requires an attribute-change walk to overlap a CPA collapse in the x86 module mapping area. `CPA_COLLAPSE` is set by `set_memory_rox()`, but the supplied context does not establish whether an ordinary local user can reliably induce both sides through module autoload or another interface.

Direct module management is generally privileged, while some module autoload requests can originate from less-privileged activity. The evidence does not resolve whether such activity can drive the complete vulnerable sequence, so `HostAdminRequired=UNKNOWN` and no privilege penalty or local-unprivileged bonus is applied.

No namespace-scoped capability chain, remote trigger, special hardware requirement, or prior configuration prerequisite is established. The race is not penalized because its practical repeatability is unresolved rather than proven difficult.

4. Primitive and severity interpretation

The exact primitive is a stale PTE pointer retained after the page-table page containing it has been freed, followed by a write through that pointer using `set_pte_atomic()`. This is an active page-table lifetime violation and an uncontrolled post-free write, not a fixed asynchronous buffer UAF or an ordinary cleanup dereference.

The primitive is CLASS_B because real kernel memory corruption exists, but attacker-directed reclaim, target selection, payload control, arbitrary read/write, or privilege escalation is not demonstrated. The supported consequence is corruption of freed or potentially reused kernel memory, with kernel failure as a plausible operational result.

`ImportantCandidate=YES` because writing through a stale page-table pointer leaves meaningful exploitation leverage unresolved. `AutoDowngradeAllowed=NO` because automatically treating this as crash-only would discard the concrete post-free write primitive. CLASS_A is not justified without controlled reuse, directed corruption, or a demonstrated security-boundary consequence.

5. One-sentence report phrase

A race between lockless CPA attribute changes and page-table collapse can cause `set_pte_atomic()` to write through a stale PTE pointer after its page-table page has been freed, creating an unresolved kernel memory corruption primitive.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Manual review should determine whether below-host-admin activity can induce both CPA operations and whether page-table-page reuse gives useful control over the stale write destination or affected kernel object.

7. Call-site confidence

Call-site confidence: medium

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

Patch: x86/mm/pat: Acquire init_mm read lock on attribute changes to avoid UAF [ Upstream
Commit: e21a9ea81426a85fdb0cdcfcc99d5d9c16b402ab
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e21a9ea81426a85fdb0cdcfcc99d5d9c16b402ab

Changed files:
  arch/x86/mm/pat/set_memory.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=e21a9ea81426a85fdb0cdcfcc99d5d9c16b402ab

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

The original Linux kernel CVE announcement for CVE-2026-97533 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97533

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:H/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 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: unknown
  Paranoid ActionableScore: 5

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).