[CVE-2026-98107][MODERATE REGULAR] Bluetooth: L2CAP: fix out-of-bounds write in l2cap_ecred_connect [ Upstream

[CVE-2026-98107][MODERATE REGULAR] Bluetooth: L2CAP: fix out-of-bounds write in l2cap_ecred_connect [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98107
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Bluetooth: L2CAP: fix out-of-bounds write in l2cap_ecred_connect [ Upstream
Commit: ce0927eb3ee2939fab5ce3f9334bfd2fafb38481
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ce0927eb3ee2939fab5ce3f9334bfd2fafb38481
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98107
Analysis date: Mon, 28 Sep 2026 08:00:37 -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-2026-98107 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98107

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-2026-98107	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98107 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-193;CWE-129;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'An incorrect channel count in the Bluetooth L2CAP ECRED connection path can allow six pending channels to be placed into a request that has space for only L2CAP_ECRED_CONN_SCID_MAX entries. The DDDDND sequence described by the change causes one __le16 value to be written beyond the SCID array in l2cap_ecred_defer_connect. The overflowing array is followed by other fields in l2cap_ecred_conn_data, including kernel pointers, so the write may corrupt adjacent state and can plausibly cause a kernel crash or more serious memory corruption. For the CVSS the PR:L value is used because a local user or process must be able to create and connect Bluetooth L2CAP sockets. The issue is not directly network reachable because the vulnerable write occurs while the local kernel constructs an outgoing ECRED connection request. Impact is at least a local denial of service and may include confidentiality or integrity impact if the adjacent pointer corruption can be made useful. The limited two byte write does not by itself prove arbitrary code execution, but the memory corruption primitive and possible local privilege escalation require manual analysis.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) 	MAYBE	REMOTE WRITE OOB LOCK RACE NETWORK TIMER  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	-	-	checked

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

ActionableScore=2
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
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 Constrained kernel buffer overwrite. The sixth `__le16` SCID is written beyond `pdu.scid`, but the destination is fixed, the overrun is exactly two bytes, and the value is a kernel-assigned SCID rather than an attacker-selected payload.
* +1 Local unprivileged trigger. An ordinary local process can use non-raw L2CAP sockets and control the deferred and non-deferred connection sequence without host-admin-equivalent privilege.
* +0 Strong corruption primitive. The write has no target selection, arbitrary payload, controlled reclaim, callback influence, or demonstrated overwrite of an active pointer.
* +0 Reliable kernel crash. The supplied evidence establishes an invalid ECRED request, not an Oops, panic, or host-wide DoS.
* +0 Confidentiality or integrity consequence. No disclosure, protected-object modification, or useful corruption of active state is demonstrated.
* +0 Practical exploitation chain. The established chain ends with the bounded overwrite and malformed outgoing request.
* No negative privilege, race, niche-subsystem, or hardware penalty was applied. The trigger does not depend on the race mentioned in the commit, and ordinary Bluetooth hardware is not inherently rare.
* Controlled reclaim, arbitrary kernel write, privilege escalation, and remote reachability are not established.

3. Reachability analysis

The evaluated attacker is an ordinary local process creating six L2CAP ECRED sockets in the specified `DDDDND` order. Non-raw L2CAP connection sockets are normally available below host-admin privilege, and the relevant deferred setup behavior is not shown to require an administrative capability.

The complete trigger requires a usable Bluetooth adapter, an appropriate peer or connection, and the ability to initiate the grouped ECRED connections. These are operational prerequisites but do not establish host-admin privilege or rare hardware. A remote Bluetooth peer alone is not shown to control the local socket creation and deferred setup sequence, so direct remote triggering is not established.

No namespace capability is needed or material to the trigger. The vulnerable count is now moved under `conn->lock`, but the documented off-by-one sequence does not require winning a race and is repeatable through ordered socket operations.

4. Primitive and severity interpretation

The exact primitive is a single two-byte write at `scid[L2CAP_ECRED_CONN_SCID_MAX]`. This is a real OOB write and therefore classified as constrained CLASS_B rather than a validation-only or bookkeeping issue.

The inner packed `pdu` contains an eight-byte ECRED request header followed by five two-byte SCIDs. Under normal structure layout, the first overflowing SCID occupies alignment padding between the 18-byte packed `pdu` and the following naturally aligned pointer fields. The supplied patch does not demonstrate that `chan`, `pid`, or another active field is overwritten. The transmitted length can nevertheless include the extra SCID, producing the documented invalid request.

This is not a UAF, stale-object access, repeated release, or refcount mutation. The demonstrated consequence is malformed protocol output. A crash or privilege escalation would require an additional mechanism not established by the source context.

ImportantCandidate is NO because the overwrite is fixed-size, fixed-location, low-control, and lacks meaningful exploitation leverage beyond the protocol error. AutoDowngradeAllowed is YES because no unresolved active-object, authorization, ownership, lifetime, or controlled-corruption primitive remains. Operational severity is ordinary Moderate or Low-like, while manual confirmation of architecture-specific layout is still prudent.

5. One-sentence report phrase

A locally triggered L2CAP ECRED counting error writes one kernel-assigned SCID beyond a fixed array and sends a malformed request, but the supplied code does not establish active pointer corruption, kernel crash, disclosure, or privilege escalation.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Confirm the exact `l2cap_ecred_conn_data` layout across supported architectures and verify that the two-byte overrun always remains within alignment padding rather than reaching `chan`, `pid`, or another active field.

7. Call-site confidence

Call-site confidence: medium

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

Patch: Bluetooth: L2CAP: fix out-of-bounds write in l2cap_ecred_connect [ Upstream
Commit: ce0927eb3ee2939fab5ce3f9334bfd2fafb38481
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ce0927eb3ee2939fab5ce3f9334bfd2fafb38481

Changed files:
  net/bluetooth/l2cap_core.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=ce0927eb3ee2939fab5ce3f9334bfd2fafb38481

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

The original Linux kernel CVE announcement for CVE-2026-98107 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98107

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:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.8

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