* [CVE-2026-98461][MODERATE REGULAR] Bluetooth: hci_sock: validate event length before filtering
@ 2026-10-24 8:14 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-10-24 8:14 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98461
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Bluetooth: hci_sock: validate event length before filtering
Commit: 39e99d85071bca0feeec3164a9437ca1bff297fc
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=39e99d85071bca0feeec3164a9437ca1bff297fc
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98461
Analysis date: Sat, 24 Oct 2026 04:14:39 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
Malformed controller or vhci HCI events can cause small pre-validation skb out-of-bounds reads without a demonstrated disclosure, write, or reliable kernel crash.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98461 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98461
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: MODERATE REGULAR
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-2026-98461 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98461 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE AEGIS_AS=1 LEGACY=MODERATE RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H';CWE-125;*CWE-20;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.9';DESCR 'Bluetooth HCI socket filtering performs reads before hci_event_packet validates the event header. An empty event can cause a read from skb data at offset zero, while truncated Command Complete and Command Status events can cause two byte reads at offsets 3 or 4 when an opcode filter is active. Masking the event code before command event identification also aliases codes above 0x3f, including event 0x4f as Command Status 0x0f. The demonstrated primitive is a small bounded out of bounds read with no evidence of an out of bounds write or UAF. For the CVSS the PR:N value applies to a malicious or faulty controller that can supply malformed HCI events without privileges on the host. The vhci path instead normally requires local access and permission to control a virtual HCI device. Direct network reachability is not established because ordinary remote Bluetooth traffic is not equivalent to controller supplied HCI event injection. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 5.9 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage IMPORTANT to MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore threshold 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 LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4. The independent weaker Aegis shadow evaluated CVSS 2.0 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) MAYBE REMOTE OOB SIMPLEFIX NETWORK SKB HARDWARE LINUS LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 2.
* Conservative score: 2; no floor or cap applied.
* Raw paranoid score: 2.
* Paranoid score: 2; stronger effects lack supporting evidence.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 weak bounded OOB-read concern: `skb->data[0]` is read for an empty skb, and two-byte opcodes are read at offsets 3 or 4 from truncated events.
* +1 firmware/device-mediated influence: a malicious or faulty Bluetooth controller can supply malformed HCI events; vhci is an alternative local injection path.
* +0 crash: the patch confirms invalid reads but not a reliable fault or host panic. These small reads may remain within skb allocation while exceeding logical length.
* No disclosure point: no out-of-range bytes are returned to the controller, socket user, or another observer.
* No write, UAF, retry-accumulated B5-R chain, shared-backing write, or corrupted active-state consumer exists.
* No remote-reachability point: ordinary over-the-air Bluetooth traffic is not shown to provide raw controller event injection.
* No authorization signal: the added checks validate packet length; they do not restore an access-control decision.
3. Reachability analysis
A malicious attached controller can trigger the malformed-event path without host-administrator powers, supporting `HostAdminRequired=NO` and `RequiresHostUID0=NO` for that attack model. The vhci route requires local permission to control a virtual HCI device, but its precise privilege and namespace requirements are not established. No direct network trigger, special race, or retry sequence is shown.
4. Primitive and severity reading
The exact primitive is a small read beyond the skb’s logical data length before `hci_event_packet()` validates the event header. It is read-only, with no demonstrated disclosure, later security-sensitive consumption, write, or ownership violation. The event-code masking bug can misclassify event 0x4f and reach the truncated opcode read, but does not create active-state corruption. This is CLASS_C invalid-read behavior; stronger confidentiality or availability consequences are speculative. Auto-downgrade remains allowed because no material unknown corruption or boundary primitive survives.
5. One-sentence report phrase
Malformed controller or vhci HCI events can cause small pre-validation skb out-of-bounds reads without a demonstrated disclosure, write, or reliable kernel crash.
6. Manual review advice
MANUAL CHECK RECOMMENDED
Confirm controller/vhci exposure and whether allocator layout makes the bounded reads fault-capable.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: Bluetooth: hci_sock: validate event length before filtering
Commit: 39e99d85071bca0feeec3164a9437ca1bff297fc
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=39e99d85071bca0feeec3164a9437ca1bff297fc
Commit description:
is_filtered_packet() reads the event code from skb->data[0] without first
checking that the skb is nonempty. When an opcode filter is configured,
it also reads the command opcode at offsets 3 or 4 without checking that
a Command Complete or Command Status event is long enough.
hci_send_to_sock() invokes the filter before hci_event_packet() validates
the event header. A malformed event supplied by a controller or a vhci
device can therefore cause an out-of-bounds read.
Keep the unmasked event code for the opcode checks. The masked value is
needed for the 64-bit event bitmap, but using it to identify command events
aliases event codes above 0x3f. In particular, Synchronous Train Complete
(0x4f) was treated as Command Status (0x0f) even though its payload has no
opcode.
Reject actual command events that are too short for the field being
inspected. A truncated command event cannot match a configured opcode.
Fixes: 1da177e ("Linux-2.6.12-rc2")
Cc: [email protected]
Signed-off-by: Aldo Ariel Panzardo <[email protected]>
Signed-off-by: Luiz Augusto von Dentz <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
net/bluetooth/hci_sock.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=39e99d85071bca0feeec3164a9437ca1bff297fc
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98461 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98461
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:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H
The Best / paranoid CVSS score: 5.9
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: 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: MODERATE
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): MODERATE REGULAR
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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