* [CVE-2026-98120][LOW] netfs: Fix subreq ref leak [ Upstream
@ 2026-09-25 12:03 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-25 12:03 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98120
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: netfs: Fix subreq ref leak [ Upstream
Commit: ebefb12122d1319257ecac01c1a928f78007716a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ebefb12122d1319257ecac01c1a928f78007716a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98120
Analysis date: Fri, 25 Sep 2026 08:03:23 -0400
ActionableScore: 2
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-2026-98120 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98120
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-2026-98120 LOW https://www.kernelcve.org/list/?q=CVE-2026-98120 CHECK WITH IMPACT FROM ORIG NN IMPORTANT Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-772;*CWE-401;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A reference leak in netfs_unbuffered_write can occur when preparation and truncation leave subreq io_iter with zero remaining length. The previous path exits the dispatch loop without terminating the subrequest, which may retain the subrequest and associated request resources and may prevent an unbuffered or direct I/O write from completing normally. For the CVSS the PR:L value is used because a local user or process must issue writes through a filesystem backed by netfs. AC:H is used because triggering depends on the iterator reaching an unexpected zero length state during subrequest preparation. The issue is not directly network reachable even when the affected netfs consumer communicates with a remote filesystem server. The demonstrated impact is limited resource leakage or a stalled write. Repeated triggering could potentially cause broader denial of service through accumulated request objects, but there is no supported UAF, OOB access, information leak, or write primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) SKIP CVE-2026-98120 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: a0b4c7a49137e YES NO NO unknown MAYBE REMOTE WRITE OOB DISK SIMPLEFIX LEAK LINUS LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 2
* Paranoid score: 2
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Concrete persistent kernel resource/reference leak. The commit directly establishes that a subrequest reference is lost when the truncated iterator has zero length and the loop exits without terminating the subrequest.
* +1 Local unprivileged trigger. A user with ordinary write access to an existing netfs-backed mount can reach the unbuffered or direct I/O write path without host-admin-equivalent privilege.
* +0 Strong DoS. The supplied evidence establishes a reference leak, but not a kernel crash, filesystem shutdown, or host-wide resource exhaustion.
* +0 Additional resource-exhaustion impact. Accumulation is conceivable, but reliable repeated triggering and host-wide exhaustion are not demonstrated.
* +0 UAF or repeated release. No object is released and then accessed or released again through a dangling reference.
* +0 Confidentiality and integrity. No disclosure, OOB access, arbitrary write, ownership violation, or other corruption primitive is established.
* +0 Remote reachability. A remote filesystem may underlie netfs, but the supplied evidence does not show that a remote server can independently create the zero-length iterator condition.
* No negative points were applied. The unexpected state is not shown to depend on a hard race, rare hardware, or host-admin-only operation.
Repeated-release checks:
* First release can end lifetime: no first release is present in the vulnerable path.
* Exact reference survives a first release: not applicable.
* Second lifetime or refcount mutation: none.
* Concrete repeated release or refcount +1: not awarded.
* Paranoid repeated-refcount leverage +1: not awarded.
* FLOOR 5: not applicable.
3. Reachability analysis
The vulnerable path is reached through an unbuffered or direct I/O write to a filesystem using netfs infrastructure. Mount creation and remote filesystem configuration normally involve prior administrative setup, but an ordinary user with write permission to an already mounted file can issue the relevant write operation. Therefore host-admin privilege is not required for the runtime path.
The supplied fragment does not establish that the complete operation is specifically enabled through attacker-created namespaces, so NamespaceScopedPrivilege remains UNKNOWN. No special hardware, boot option, race, or firmware interaction is identified. The attacker can issue writes but does not appear to directly control the internal subrequest reference or its termination state. Whether the zero-length iterator condition can be forced repeatedly and reliably is unresolved.
4. Primitive and severity interpretation
The exact primitive is a missing subrequest termination that leaves an acquired kernel reference and associated resources unreleased. This is a resource-lifetime leak, not a post-lifetime access.
There is no active or fixed stale storage because no freed object is subsequently used. The defect occurs in an exceptional preparation branch, but it does not perform a second put, release, free, or refcount mutation. It is therefore not a repeated-lifetime Class B case.
PrimitiveClass is CLASS_C because the demonstrated security behavior is limited to a resource leak and possible request-completion or availability degradation. The practical consequence is per-event leakage. Broader resource exhaustion remains possible only if the condition is repeatable at useful scale, which is not established by the patch.
ImportantCandidate is NO because there is no corruption, UAF, security-boundary bypass, persistent cross-ownership effect, or demonstrated host-wide DoS. AutoDowngradeAllowed is YES because no unresolved exploitation primitive would be lost by treating the issue as an ordinary resource-management defect.
5. One-sentence report phrase
A zero-length iterator in netfs_unbuffered_write could bypass subrequest termination and leak a kernel reference, but the supplied evidence supports only limited resource or I/O availability impact without UAF, memory corruption, or privilege escalation.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch establishes a bounded bug class with no corruption or authorization primitive, and the evidence does not demonstrate reliable host-wide exhaustion.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: netfs: Fix subreq ref leak [ Upstream
Commit: ebefb12122d1319257ecac01c1a928f78007716a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ebefb12122d1319257ecac01c1a928f78007716a
Changed files:
fs/netfs/direct_write.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=ebefb12122d1319257ecac01c1a928f78007716a
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98120 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98120
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:N/I:N/A:L
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
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: unknown
Paranoid ActionableScore: 2
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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