[CVE-2026-93140][LOW] udf: Mark LVID buffer as uptodate before marking it dirty [ Upstream

[CVE-2026-93140][LOW] udf: Mark LVID buffer as uptodate before marking it dirty [ Upstream

[AL-KERNEL]

CVE: CVE-2026-93140
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: udf: Mark LVID buffer as uptodate before marking it dirty [ Upstream
Commit: e6461ef34f91ad7dbffdf912b3d661a7dd892931
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e6461ef34f91ad7dbffdf912b3d661a7dd892931
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93140
Analysis date: Fri, 18 Sep 2026 05:52:56 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A UDF LVID buffer can remain marked not uptodate after a block write EIO, causing later remount or sync paths to trigger a spurious mark_buffer_dirty warning, with practical impact limited to local warning or possible panic_on_warn DoS under administrative storage control.

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

The original Linux kernel CVE announcement for CVE-2026-93140 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93140

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-2026-93140	LOW	https://www.kernelcve.org/list/?q=CVE-2026-93140 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-703;CWE-754;CWE-667;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'A UDF LVID buffer can remain marked as not uptodate after a block write EIO even though the in memory LVID contents are still valid. Later remount read-write or sync paths can modify the LVID and call mark_buffer_dirty, which triggers a WARN in fs buffer code because the buffer state no longer matches the intended in memory update. For the CVSS the PR:H is used because reliable triggering normally requires administrative control over mounting or reconfiguring a UDF filesystem and inducing block device write errors. The issue is not network reachable and does not provide a demonstrated memory corruption primitive. Impact is mainly a local warning and possible denial of service on systems configured to panic on warnings.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)  SKIP CVE-2026-93140 UNKNOWN SKIP The required patch already applied both for rhel8 and for rhel9: fb0601134c7e51728bd098abc6909315de1e5d86 YES  YES YES unknown 	MAYBE	DISK WARNONLY HARDWARE LINUS SYZBOT 	-	-	checked

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

ActionableScore=1
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

## 1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate**::

No floor or cap changed the score.

## 2. Signal breakdown

Positive signals:

* +1: Kernel warning reachable in a filesystem update path after prior block write EIO leaves the LVID buffer marked not uptodate. This is a concrete invalid state leading to WARN_ON_ONCE in mark_buffer_dirty.

Negative or limiting signals:

* No UAF, stale object use, OOB access, double free, refcount corruption, arbitrary write, or controlled memory corruption is established.
* No confidentiality or integrity impact is established.
* No remote reachability is established.
* No security boundary bypass is established.
* Host-admin-equivalent filesystem and block-device control appears required for reliable triggering.
* WARN_ON alone is not counted as strong DoS except in environments configured with panic_on_warn.

Repeated release or refcount analysis:

* First release can end lifetime: no.
* Exact same reference survives to second lifetime mutation: no.
* Second lifetime/refcount mutation exists: no.
* Concrete repeated release/refcount +1 awarded: no.
* Paranoid repeated-refcount leverage +1 awarded: no.
* FLOOR 5 applied: no.

## 3. Reachability analysis

The visible trigger path involves UDF filesystem remount read-write or sync after a prior block write EIO affecting the LVID buffer. The trace goes through fsconfig and reconfigure_super, which normally requires CAP_SYS_ADMIN or equivalent filesystem administration authority.

Reliable reproduction also appears to require control over the mounted UDF filesystem and the underlying block device error behavior, such as loop or fault injection style setup. That makes HostAdminRequired=YES for the supplied scenario. The input does not establish that the complete mount, reconfigure, block-device error, and sync sequence is namespace-scoped, so NamespaceScopedPrivilege=UNKNOWN.

There is no network trigger. There is no meaningful race. No special rare hardware is required, but administrative storage setup is material.

## 4. Primitive and severity interpretation

The exact issue is a buffer state consistency problem. A previous write EIO clears BH_Uptodate, but the in-memory LVID contents remain valid. Later UDF paths update the same buffer and call mark_buffer_dirty, causing a warning because the buffer flag state does not match the intended in-memory update.

PrimitiveClass=NONE because no meaningful corruption, lifetime violation, authorization bypass, ownership violation, or disclosure primitive is established. The demonstrated consequence is a spurious kernel warning. The practical security consequence is at most local DoS on systems where WARN_ON is fatal through panic_on_warn.

ImportantCandidate=NO because there is no unresolved memory corruption or boundary primitive. AutoDowngradeAllowed=YES because the issue is warning or DoS-only, privilege-gated, and lacks meaningful exploitation leverage beyond the warning path.

## 5. One-sentence report phrase

A UDF LVID buffer can remain marked not uptodate after a block write EIO, causing later remount or sync paths to trigger a spurious mark_buffer_dirty warning, with practical impact limited to local warning or possible panic_on_warn DoS under administrative storage control.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch fixes a warning-only buffer state mismatch with no demonstrated memory corruption, UAF, authorization bypass, information leak, or privilege escalation primitive.

## 7. Call-site confidence

Call-site confidence: high

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

Patch: udf: Mark LVID buffer as uptodate before marking it dirty [ Upstream
Commit: e6461ef34f91ad7dbffdf912b3d661a7dd892931
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e6461ef34f91ad7dbffdf912b3d661a7dd892931

Changed files:
  fs/buffer.c
  fs/udf/super.c
  fs/super.c
  fs/fsopen.c
  arch/x86/entry/syscall_64.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=e6461ef34f91ad7dbffdf912b3d661a7dd892931

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

The original Linux kernel CVE announcement for CVE-2026-93140 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93140

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:H/UI:N/S:U/C:N/I:N/A:L
  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: 1

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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).