* [CVE-2026-99067][LOW] btrfs: scrub: fix local_root reference leak in scrub_print_warning_inode()
@ 2026-10-27 5:28 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-10-27 5:28 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-99067
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: btrfs: scrub: fix local_root reference leak in scrub_print_warning_inode()
Commit: 41cabfbf3532e2a2a17be9e4876042a5393b5c8d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=41cabfbf3532e2a2a17be9e4876042a5393b5c8d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99067
Analysis date: Tue, 27 Oct 2026 01:28:01 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
A failed inode-path lookup during Btrfs scrub warning generation leaks one filesystem-root reference, with no demonstrated corruption, UAF, or reliable host-wide exhaustion.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99067 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99067
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-2026-99067 LOW https://www.kernelcve.org/list/?q=CVE-2026-99067 CHECK WITH IMPACT FROM ORIG NN NONE | AEGIS IMPACT MODERATE AEGIS_AS=0 LEGACY=LOW RESULT=DIFF (final Legacy and Aegis differ; FINAL: LOW, Aegis: MODERATE) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';*CWE-772;CWE-404;BEST CVSS score: '1.9';DESCR 'A reference leak occurs in scrub_print_warning_inode when btrfs_get_fs_root succeeds but paths_from_inode fails and local_root is not released. The demonstrated primitive is resource retention only and there is no evidence of UAF, OOB access, information disclosure, arbitrary write, or an immediate kernel crash. For the CVSS the PR:H value reflects that reliable triggering normally requires control of a privileged Btrfs scrub operation and filesystem state that makes inode path resolution fail. Availability impact is Low because root related resources can remain retained, but repeatable host wide resource exhaustion is not established. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 1.9 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage LOW to LOW because the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 0 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The models disagreed but the aggregation rules retained the production result. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE DISK WARNONLY SIMPLEFIX LEAK SKIP V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 1.
* Conservative score: 1.
* Raw paranoid score: 1.
* Paranoid score: 1.
* No floor or cap applies.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Concrete persistent kernel reference leak: `btrfs_get_fs_root()` supplies `local_root`, but the `paths_from_inode()` failure branch previously reached `err` without `btrfs_put_root(local_root)`. The patch adds the missing put.
* +0 Strong DoS: repeated retention is possible, but neither host-wide exhaustion nor a reliable crash is established.
* No UAF, OOB access/write, repeated release, attacker-controlled corruption, disclosure, authorization bypass, or protected-state modification is shown.
* B5-R does not apply: there is no heap OOB write or later consumption of corrupted structured state.
* B3-PENDING does not apply: no shared-backing write exists.
* B4-PENDING does not apply: the patch repairs resource cleanup, not a DENY-to-ALLOW authorization decision.
3. Reachability analysis
The vulnerable function runs while reporting Btrfs scrub warnings, and failure of inode path resolution reaches the leak. The supplied evidence does not positively establish the complete trigger permissions. The legacy hints suggest privileged scrub control is normally involved, but that is insufficient to prove a host-admin-only requirement or justify a privilege penalty. Namespace-scoped reachability, ordinary-user triggering, prior setup requirements, and reliable attacker control over repeated failures are unproven. No race or special hardware is involved.
4. Primitive and severity reading
The exact primitive is a missing root-reference release on one error path. It causes resource retention, not stale post-lifetime use: the object remains referenced rather than being freed too early. This is CLASS_C resource-management behavior, with no demonstrated memory corruption or immediate crash. Accumulated resource pressure is plausible but unquantified. There is no Important-grade primitive, so automatic downgrade is allowed.
5. One-sentence report phrase
A failed inode-path lookup during Btrfs scrub warning generation leaks one filesystem-root reference, with no demonstrated corruption, UAF, or reliable host-wide exhaustion.
6. Manual review advice
NO MANUAL CHECK NEEDED
The patch shows a narrow reference leak with no unresolved security-boundary or corruption primitive.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: btrfs: scrub: fix local_root reference leak in scrub_print_warning_inode()
Commit: 41cabfbf3532e2a2a17be9e4876042a5393b5c8d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=41cabfbf3532e2a2a17be9e4876042a5393b5c8d
Commit description:
When paths_from_inode() fails, scrub_print_warning_inode() jumps to err
without dropping the reference taken by btrfs_get_fs_root(), leaking a
reference to the root every time path resolution fails while printing
scrub warnings. Every other error and success path of the function
drops the reference.
Drop the reference on the paths_from_inode() failure path too.
Fixes: 558540c ("btrfs scrub: print paths of corrupted files")
CC: [email protected]
Reviewed-by: Qu Wenruo <[email protected]>
Signed-off-by: Wentao Liang <[email protected]>
Reviewed-by: David Sterba <[email protected]>
Signed-off-by: David Sterba <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
fs/btrfs/scrub.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=41cabfbf3532e2a2a17be9e4876042a5393b5c8d
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99067 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99067
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: Not available
The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS score: 1.9
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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