* [CVE-2026-93232][LOW] mm/hugetlb: fix boot panic with CONFIG_DEBUG_VM and HVO bootmem pages
@ 2026-09-24 16:05 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-24 16:05 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-93232
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: mm/hugetlb: fix boot panic with CONFIG_DEBUG_VM and HVO bootmem pages
Commit: 2ddf429e25cf8415d9c308f07e64012026bd4d77
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2ddf429e25cf8415d9c308f07e64012026bd4d77
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93232
Analysis date: Thu, 24 Sep 2026 12:05:46 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-93232 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93232
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: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-93232 LOW https://www.kernelcve.org/list/?q=CVE-2026-93232 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:H/UI:N/S:U/C:N/I:N/A:H';CWE-665;*CWE-457;CWE-754;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.4';DESCR 'A boot time kernel panic can occur because shared vmemmap tail struct pages are initialized after bootmem HugeTLB folios may already access their pageblock state. The issue requires CONFIG_DEBUG_VM together with HugeTLB vmemmap optimization, bootmem gigantic hugepages, and hugetlb_free_vmemmap enabled. The resulting failure occurs during kernel startup and can prevent the system from completing the boot process. For the CVSS the PR:H value is used because reliable triggering requires administrative control over the kernel build or boot configuration. The issue is not network reachable and cannot be triggered by ordinary runtime packet or user input. Impact is denial of service through boot failure. The examined code does not provide a UAF, OOB access, information disclosure, or write primitive that would support confidentiality, integrity, or privilege escalation impact.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) SKIP CVE-2026-93232 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE READ INIT HARDWARE LINUS MEMORY DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: -2
* Conservative score: 0
* Raw paranoid score: -2
* Paranoid score: 0
* Applied score normalization: -2 -> 0 because ActionableScore has a minimum of 0.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Reliable kernel crash / strong DoS. The uninitialized shared tail page can cause a boot-time panic on an affected configuration.
* -2 Full host-admin-equivalent privilege. Deliberate triggering requires control over the kernel build or boot configuration.
* -1 Rare and difficult-to-reach configuration. The path requires CONFIG_DEBUG_VM, HVO, bootmem gigantic HugeTLB pages, and hugetlb_free_vmemmap.
* No UAF, OOB access, write primitive, controlled corruption, repeated release, or ownership violation is established.
* No confidentiality or integrity signal is awarded.
* No remote or ordinary local-user reachability is established.
* No extra Availability point is awarded because it would duplicate the same boot panic.
* The paranoid score is not increased because no stronger technically defensible primitive exists.
3. Reachability analysis
The failure occurs during early kernel initialization rather than through a runtime user-facing interface. An attacker cannot reach it through network traffic, namespaces, syscalls, or ordinary HugeTLB activity after boot. Reliable intentional triggering requires host-administrator control over the kernel configuration and boot parameters, including the affected debug and HVO configuration and bootmem gigantic hugepage setup.
The complete trigger is not namespace-scoped. No special physical hardware is identified, but the required build and boot configuration is unusual and cannot be instantiated by an ordinary user. There is no race or repeatable runtime trigger.
4. Primitive and severity interpretation
The exact primitive is access to incompletely initialized shared `struct page` tail metadata followed by a CONFIG_DEBUG_VM assertion failure and boot panic. This is an initialization-order defect and invalid-state DoS, not a lifetime violation.
There is no freed object, stale post-lifetime reference, repeated refcount mutation, active-object replacement, or attacker-controlled payload. The patch supports CLASS_C because the demonstrated result is a boot-time fatal failure without an independently useful corruption primitive.
ImportantCandidate is NO because no exploitation leverage beyond boot failure is established. AutoDowngradeAllowed is YES because the issue is configuration-specific, requires host-admin-equivalent control, and exposes no unresolved memory-corruption or security-boundary primitive. Operationally, it is a boot reliability defect with Low-like security relevance.
5. One-sentence report phrase
Incorrect initialization ordering for shared HugeTLB vmemmap tail pages can panic CONFIG_DEBUG_VM kernels during boot, but triggering requires host-controlled build and boot settings and exposes no memory-corruption or privilege-escalation primitive.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The issue is a narrowly configured boot-time assertion failure with no runtime attacker path, UAF, OOB access, authorization bypass, or confidentiality and integrity impact.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: mm/hugetlb: fix boot panic with CONFIG_DEBUG_VM and HVO bootmem pages
Commit: 2ddf429e25cf8415d9c308f07e64012026bd4d77
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2ddf429e25cf8415d9c308f07e64012026bd4d77
Commit description:
Patch series "mm: Refactor bootmem gigantic hugepage allocation", v4.
This series is split out from the earlier larger series "mm: Generalize
HVO for HugeTLB and device DAX" [1]. It collects the first 19 patches of
that series as a standalone set of fixes and preparatory cleanups around
bootmem HugeTLB handling, sparse initialization ordering, and related
vmemmap setup.
The first patches fix a few bugs found while reviewing the existing code,
including incorrect bootmem HVO handling, wrong vmemmap registration
arguments, a powerpc compound-vmemmap tracking bug, and too-late
initialization of gigantic bootmem HugeTLB struct pages.
The rest of the series reorders early memory initialization so the
relevant zone state is available before sparse and HugeTLB boot-time setup
runs, then simplifies the remaining bootmem gigantic hugepage allocation
path and removes code made obsolete by that rework.
At a high level:
- patches [1-4] fix boot-time and arch-specific bugs
- patches [5-12] reorder and simplify sparse/mm/hugetlb early init
- patches [13-19] refactor bootmem gigantic hugepage allocation and
remove obsolete helpers and state
This patch (of 19):
Commit 622026e ("mm/hugetlb: remove fake head pages") switched
HVO to reuse per-zone shared tail pages from zone->vmemmap_tails[].
Those shared tail pages were initialized in hugetlb_vmemmap_init(), but
bootmem HugeTLB folios are prepared earlier from
gather_bootmem_prealloc(). With hugetlb_free_vmemmap=on,
prep_and_add_bootmem_folios() can access pageblock flags on bootmem
HugeTLB pages whose mirrored tail struct pages already point to the shared
tail page. On CONFIG_DEBUG_VM kernels, get_pfnblock_bitmap_bitidx() then
dereferences the still-uninitialized shared tail page and can panic during
boot.
Initialize zone->vmemmap_tails[] from gather_bootmem_prealloc(), before
bootmem HugeTLB folios are processed, and drop the later initialization
from hugetlb_vmemmap_init().
This bug only affects CONFIG_DEBUG_VM kernels, where the relevant
assertion is evaluated.
Link: https://lore.kernel.org/[email protected]
Link: https://lore.kernel.org/[email protected]
Fixes: 622026e ("mm/hugetlb: remove fake head pages")
Signed-off-by: Muchun Song <[email protected]>
Acked-by: Oscar Salvador <[email protected]>
Tested-by: Michal Clapinski <[email protected]>
Reviewed-by: Michal Clapinski <[email protected]>
Cc: "Aneesh Kumar K.V" <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Madhavan Srinivasan <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Nicholas Piggin <[email protected]>
Cc: "Ritesh Harjani (IBM)" <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Frank van der Linden <[email protected]>
Cc: Oscar Salvador (SUSE) <[email protected]>
Cc: Usama Arif <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
mm/hugetlb.c
mm/hugetlb_vmemmap.c
mm/sparse-vmemmap.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=2ddf429e25cf8415d9c308f07e64012026bd4d77
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-93232 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93232
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:N/I:N/A:H
The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
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: unknown
Paranoid ActionableScore: 0
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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