* [CVE-2026-99241][IMPORTANT] ntfs: take invalidate_lock in ntfs_filemap_page_mkwrite() [ Upstream
@ 2026-11-03 3:10 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-11-03 3:10 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-99241
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: NO
Patch: ntfs: take invalidate_lock in ntfs_filemap_page_mkwrite() [ Upstream
Commit: 57c0d5281666d150c73e56e6795a4eef3ede8693
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=57c0d5281666d150c73e56e6795a4eef3ede8693
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99241
Analysis date: Mon, 02 Nov 2026 23:10:03 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
A local writable-file race lets NTFS page-mkwrite consume stale runlist mappings during invalidation, risking disk-cluster corruption and requiring review for unresolved cross-file impact.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99241 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99241
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: IMPORTANT
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-2026-99241 IMPORTANT https://www.kernelcve.org/list/?q=CVE-2026-99241 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=IMPORTANT RESULT=DIFF INDEPENDENT_LEGACY=IMPORTANT INDEPENDENT_RESULT=DIFF TEMP_KPANIC_MERGE=IMPORTANT_WINS_DISAGREEMENT PRE_MERGE_LEGACY=IMPORTANT (final Legacy and Aegis differ; FINAL: IMPORTANT, Aegis: MODERATE_KPANIC) 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-362;CWE-367;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A race in ntfs_filemap_page_mkwrite allows an mmap write fault to run while truncate or fallocate changes the page cache, runlist, and disk cluster allocation. The resulting stale block mapping can plausibly dirty or write clusters that are being freed, reallocated, or not yet zeroed, creating filesystem corruption, cross file integrity impact, availability loss, and a possible stale data disclosure window. The demonstrated primitive is filesystem mapping inconsistency rather than kernel heap UAF or OOB memory corruption. For the CVSS the PR:L value is selected because an attacker needs local user access with permission to map and modify the affected file, but does not normally need administrative privileges. AC:H is selected because exploitation requires coordinating concurrent operations within a race window. The issue is not directly network reachable unless a separate service exposes the required file and allocation operations. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 5 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage IMPORTANT to IMPORTANT because KP specialist did not establish a qualifying panic. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist produced a review artifact and its decision was processed by the applicable downgrade and preservation rules. Exact triggered rule markers were TEMP_KPANIC_MERGE_IMPORTANT_WINS and KPANIC_UNSUPPORTED_REMOVED. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 2 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is IMPORTANT.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) MAYBE WRITE OOB LOCK DISK SIMPLEFIX RACE LEAK IMPROVEONLY LINUS TEMP_KPANIC_MERGE_IMPORTANT_WINS KPANIC_UNSUPPORTED_REMOVED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 4.
* Conservative score: 4; no floor or cap applied.
* Raw paranoid score: 5.
* Paranoid score: 5; adds the credible but unresolved cross-file integrity consequence.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
* +1 Local unprivileged trigger: a user permitted to mmap-write and resize the affected file can invoke the racing operations without host administration.
* +1 Weak/indirect corruption candidate: `iomap_page_mkwrite()` can consume block mappings while truncate/fallocate invalidates page cache and rewrites the runlist.
* +1 Filesystem/storage corruption path: the race can dirty mappings while clusters are being allocated, zeroed, or freed.
* +1 Important filesystem path: page-cache, extent/runlist, and on-disk cluster ownership are involved.
* Paranoid +1 Integrity plausible: a stale mapping may write a cluster after it is freed or reallocated, creating a technically credible cross-file ownership impact. The supplied evidence does not identify a victim file or prove that reallocation occurs.
* No race penalty: concurrency is required, but the actor can repeatedly drive both file operations; a narrow uncontrollable window is not shown.
* No crash/availability point: filesystem damage is plausible, but a reliable crash or shutdown is not demonstrated.
* No UAF, heap OOB write, arbitrary write, controlled target, disclosure, or LPE is shown. B5-R and B3-PENDING do not apply.
3. Reachability analysis
The supported actor is a local user with write and resize authority over an NTFS file. Host UID 0 and host-administrator capabilities are not required for that file-local trigger. Mounting the filesystem is prior administrative setup, but not a separate per-trigger privilege requirement. Namespace-scoped capability reachability is not established. The race is repeatable through concurrent mmap faults and truncate/fallocate operations; direct remote reachability is not shown.
4. Primitive and severity reading
The primitive is an active filesystem mapping-consistency breach, not kernel-memory corruption: page-mkwrite consumes an active runlist/block mapping without the invalidate lock while another operation changes page-cache and extent ownership. The later privileged consumers are iomap/page-cache and filesystem block-I/O paths. The unresolved boundary is whether stale cluster ownership crosses from the attacker-controlled file into another file’s allocation.
This is CLASS_B. File-local stale mapping and dirtying are supported; protected-victim corruption, stale-data disclosure, panic, and arbitrary disk writes remain unproven. ImportantCandidate is YES and auto-downgrade is disallowed because the active corrupted mapping is consumed and a specific cross-file ownership boundary remains credible but unresolved.
5. One-sentence report phrase
A local writable-file race lets NTFS page-mkwrite consume stale runlist mappings during invalidation, risking disk-cluster corruption and requiring review for unresolved cross-file impact.
6. Manual review advice
MANUAL CHECK REQUIRED
Confirm whether a freed or newly allocated cluster can be dirtied after ownership transfers to another inode, and whether stale data can be exposed before zeroing completes.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: ntfs: take invalidate_lock in ntfs_filemap_page_mkwrite() [ Upstream
Commit: 57c0d5281666d150c73e56e6795a4eef3ede8693
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=57c0d5281666d150c73e56e6795a4eef3ede8693
Changed files:
fs/ntfs/file.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=57c0d5281666d150c73e56e6795a4eef3ede8693
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99241 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99241
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: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: 4
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: IMPORTANT
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): IMPORTANT
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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