* [CVE-2026-98082][LOW] btrfs: fix the possible bioc_list memory leak during error [ Upstream
@ 2026-09-25 19:10 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-25 19:10 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98082
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: btrfs: fix the possible bioc_list memory leak during error [ Upstream
Commit: 83f0c973cffb184d019390ffdb5d31de5c85bc61
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=83f0c973cffb184d019390ffdb5d31de5c85bc61
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98082
Analysis date: Fri, 25 Sep 2026 15:10:08 -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-2026-98082 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98082
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-2026-98082 LOW https://www.kernelcve.org/list/?q=CVE-2026-98082 CHECK WITH IMPACT FROM ORIG NN NONE 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-401;*CWE-772;**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 memory leak can occur when btrfs_io_context objects remain attached to an ordered extent after btrfs_insert_one_raid_extent fails or when BTRFS_ORDERED_IOERR causes raid extent insertion to be skipped. Repeated failures on a Btrfs filesystem using RAID_STRIPE_TREE can accumulate unreleased bioc objects and gradually consume kernel memory. For the CVSS the PR:L value is used because a local user or process with write access to the affected filesystem may generate the workload, although reliable triggering also depends on filesystem configuration and error conditions. The issue is not directly network reachable. A network service backed by the affected filesystem could provide an indirect workload source, but the required storage errors are not normally controlled by a remote client. The realistic impact is limited resource consumption with A:L. The paranoid impact is A:H because sustained failures may eventually exhaust memory and cause a system wide denial of service. No UAF, OOB access, information disclosure, or write primitive is visible in the affected paths.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) MAYBE DISK LEAK SKIP - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
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 error paths leave `btrfs_io_context` references on `ordered_extent->bioc_list` without the required `btrfs_put_bioc()`.
* +1 Important filesystem/storage path. The defect affects Btrfs ordered-extents and RAID stripe extent processing.
* No additional resource-exhaustion point. Accumulation is possible, but the supplied evidence does not establish rapid host-wide exhaustion, an accounting bypass, or persistent unavailability.
* No reliable-crash point. Neither the commit nor the diff demonstrates a panic, filesystem shutdown, or fatal fault.
* No UAF or repeated-release signal. The vulnerable paths omit releases rather than releasing an object and later using or releasing the same dangling reference.
* No arbitrary write, OOB access, controlled corruption, disclosure, COW violation, or authorization bypass is established.
* No remote-reachability point. A network-backed workload may indirectly generate writes, but remote control over the required Btrfs insertion or I/O failure is not established.
* No privilege penalty. Host-admin privilege is required to configure the filesystem feature, but the evidence does not establish that host-admin-equivalent privilege is required for the complete runtime trigger.
3. Reachability analysis
The affected filesystem must use the `RAID_STRIPE_TREE` incompatibility feature, which requires prior filesystem provisioning or configuration by an administrator. The leak occurs when RAID extent insertion fails or when an ordered extent receives `BTRFS_ORDERED_IOERR`.
A local process with write access may generate the surrounding I/O workload, but the supplied evidence does not show that an ordinary user can reliably cause either required error condition. Conversely, it does not prove that the runtime trigger itself requires host administration. Therefore `HostAdminRequired=UNKNOWN`.
No user-namespace or namespace-scoped capability path is established. No special hardware is inherently required, although storage failures can provide one of the triggering conditions. This is an ordered error-path defect, not a race, so no timing penalty applies.
4. Primitive and severity interpretation
The exact defect is a missing cleanup operation that produces a persistent kernel reference and memory leak. `btrfs_io_context` objects remain linked to an ordered extent without receiving the corresponding `btrfs_put_bioc()` when insertion fails or is skipped after an I/O error.
This is not a stale post-lifetime access. The objects remain referenced too long rather than being freed too early. There is no first release that may destroy an object, no surviving dangling reference, and no second lifetime or refcount mutation. The repeated-release exception and UAF score floors therefore do not apply.
`PrimitiveClass=NONE` because no corruption, post-lifetime use, ownership violation, authorization bypass, or comparable exploitation primitive is established. The demonstrated defect is a resource leak. Repeated failures could gradually increase kernel memory consumption, but immediate or host-wide exhaustion is not demonstrated.
`ImportantCandidate=NO` because there is no Important-grade primitive or unresolved corruption leverage. `AutoDowngradeAllowed=YES` because the issue is a bounded-class resource-management defect without UAF, memory corruption, security-boundary bypass, or demonstrated strong DoS. The likely operational severity is Low to ordinary Moderate.
5. One-sentence report phrase
Btrfs can leak btrfs_io_context references when RAID stripe extent insertion fails or is skipped after an ordered extent I/O error, allowing repeated failures to cause gradual kernel memory consumption without an established corruption or privilege escalation primitive.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch establishes a conventional missing-cleanup memory leak with no UAF, corruption, boundary bypass, or demonstrated rapid host-wide exhaustion.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: btrfs: fix the possible bioc_list memory leak during error [ Upstream
Commit: 83f0c973cffb184d019390ffdb5d31de5c85bc61
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=83f0c973cffb184d019390ffdb5d31de5c85bc61
Changed files:
fs/btrfs/inode.c
fs/btrfs/raid-stripe-tree.c
fs/btrfs/raid-stripe-tree.h
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=83f0c973cffb184d019390ffdb5d31de5c85bc61
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98082 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98082
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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