[CVE-2026-90092][MODERATE 7.0] Bluetooth: L2CAP: reject accept queue add unless BT_LISTEN [ Upstream

[CVE-2026-90092][MODERATE 7.0] Bluetooth: L2CAP: reject accept queue add unless BT_LISTEN [ Upstream

[AL-KERNEL]

CVE: CVE-2026-90092
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: Bluetooth: L2CAP: reject accept queue add unless BT_LISTEN [ Upstream
Commit: bf61a65c6093970e3b50031c4b79ebf3bd411eba
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bf61a65c6093970e3b50031c4b79ebf3bd411eba
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90092
Analysis date: Fri, 18 Sep 2026 03:46:48 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

======================================================================
ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-90092 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90092

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 7.0
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-90092	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-90092 CHECK WITH IMPACT FROM ORIG NN 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:H/I:H/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.5';DESCR 'A race in the Bluetooth L2CAP socket path can allow l2cap_sock_new_connection_cb to add a new child socket after the parent listener has completed teardown and entered BT_CLOSED. The child socket may retain a dangling parent reference, and later dereferencing that reference can result in use after free and a kernel crash. A nearby Bluetooth peer may be able to trigger the race by initiating an L2CAP connection while the listening socket is being closed. For the CVSS the PR:N value is used because no account or local privileges on the target are required when the attacker can directly reach the exposed Bluetooth L2CAP service. AV:A is used because exploitation requires Bluetooth proximity or equivalent adjacent radio access rather than general Internet reachability. AC:H reflects the timing dependent race between connection creation and listener teardown. Impact is at least denial of service through a kernel crash. In the worst still defensible case, reuse of the freed socket object may affect confidentiality and integrity or potentially support privilege escalation, although a reliable arbitrary read or write primitive is not demonstrated.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)  SKIP CVE-2026-90092 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	REMOTE LOCK NULLPTR INIT RACE UAF NETWORK SYZBOT KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH	-	-	checked

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

ActionableScore=5
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 5
* Conservative score: 5
* Raw paranoid score: 5
* Paranoid score: 5
* No floor or cap changed either score. FLOOR 5 is consistent with the escaping active-object UAF, but the raw score already reaches 5.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Positive signals:

* +2 Real UAF and lifetime violation. A child socket can retain `bt_sk(sk)->parent` after the parent listener is killed, creating a concrete dangling reference that is later dereferenced.
* +2 Direct network trigger. A nearby Bluetooth peer can reach the vulnerable connection path by initiating an L2CAP connection against an existing listener. This is adjacent wireless reachability rather than Internet-wide reachability.
* +1 Reliable kernel crash or strong DoS. Dereferencing the dangling parent socket can cause a kernel fault and system denial of service.

Negative signals:

* No timing penalty. The bug is a race, but the supplied evidence does not establish that the timing window is exceptionally narrow, one-shot, or impractical to retry.
* No privilege penalty. The external Bluetooth peer does not need an account, local execution, or host-administrator privilege on the target.

Material signals not awarded:

* Controlled reclaim or attacker-shaped replacement contents are not demonstrated.
* Arbitrary or directed kernel read or write is not demonstrated.
* Strong LPE leverage is not awarded merely because this is a UAF.
* Structured stale-object leverage is not separately awarded because the supplied context establishes a dangling parent dereference but does not show meaningful consumption of attacker-influenced replacement fields.
* Attacker-influenced lifetime manipulation is not awarded because the peer controls connection attempts but is not shown to control parent-listener teardown.
* No concrete repeated release, put, free, or refcount mutation on the same dangling reference is shown.
* The first parent destruction can end its lifetime, but no second lifetime-mutating operation on that exact parent reference is established.
* Concrete repeated release/refcount +1 was not awarded.
* Paranoid repeated-refcount leverage +1 was withheld.
* Weak LPE was not awarded from theoretical allocator reuse.
* Confidentiality and integrity points were not awarded because no disclosure, controlled write, callback influence, or useful post-reclaim operation is established.
* Extra Availability was not awarded because the kernel crash is already counted.
* FLOOR 5 required no arithmetic adjustment.

3. Reachability analysis

The evaluated attacker is a nearby Bluetooth peer that can initiate an L2CAP connection to an existing listening service. The vulnerable interleaving occurs when that connection is processed while the parent listener is being closed. The peer controls connection attempts but is not shown to control the listener teardown directly.

No target account or host-administrator privilege is required for the network-side attacker, so `HostAdminRequired=NO`. Bluetooth proximity or equivalent adjacent radio access is required. This is not general Internet reachability.

An existing L2CAP listener and an enabled Bluetooth adapter are prerequisites, but the supplied evidence does not establish that creating the relevant listener necessarily requires host-admin-equivalent privilege. It also does not establish a user-namespace or network-namespace capability chain, so `NamespaceScopedPrivilege=UNKNOWN`.

The race appears retryable through repeated connection attempts, but successful triggering still depends on overlap with listener teardown. The evidence does not justify either a hard-race penalty or an additional repeatability bonus.

4. Primitive and severity interpretation

The exact primitive is an escaping dangling reference from a newly created child socket to a parent L2CAP socket whose lifetime may already have ended. This is an active structured-object UAF rather than fixed stale storage.

The stale reference is created during normal connection handling and can survive beyond parent teardown. Its later dereference is broader than an immediate destructor-only stale access. However, the available context demonstrates a crash-capable stale parent dereference, not controlled reclaim, attacker-shaped replacement, callback dispatch, arbitrary access, or a second refcount mutation.

There is no concrete repeated-release pattern. The parent can be destroyed by `l2cap_sock_kill`, but the shown stale operation is a later dereference through the child rather than a second `put`, `release`, `free`, or equivalent lifetime mutation on the exact parent reference.

This is `CLASS_B` because a real active-object lifetime violation exists and crosses the connection and teardown paths. The demonstrated consequence is kernel crash and DoS. Confidentiality impact, integrity impact, and privilege escalation remain theoretical and are not scored.

`ImportantCandidate=YES` because this is a remotely influenced active socket UAF whose complete post-lifetime use and reclaim behavior remain unresolved. `AutoDowngradeAllowed=NO` because automatically treating it as an ordinary crash would discard a concrete escaping kernel lifetime primitive. The evidence nevertheless supports Actionable Moderate rather than Strong Important because no independently useful exploitation leverage beyond the stale dereference has been established.

5. One-sentence report phrase

A nearby Bluetooth peer can race an incoming L2CAP connection with listener teardown, leaving a child socket with a dangling parent reference that may be dereferenced after free and crash the kernel.

6. Manual review recommendation

MANUAL CHECK REQUIRED

The active socket UAF is adjacent-network reachable and escapes the immediate teardown path, but reclaim behavior and later uses of the dangling parent require source-level review before ruling out impact beyond DoS.

7. Call-site confidence

Call-site confidence: high

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

Patch: Bluetooth: L2CAP: reject accept queue add unless BT_LISTEN [ Upstream
Commit: bf61a65c6093970e3b50031c4b79ebf3bd411eba
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bf61a65c6093970e3b50031c4b79ebf3bd411eba

Changed files:
  net/bluetooth/l2cap_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=bf61a65c6093970e3b50031c4b79ebf3bd411eba

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

The original Linux kernel CVE announcement for CVE-2026-90092 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90092

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:H/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.5

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: 5

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: YES
Published priority for this report (same as in Subject): MODERATE 7.0

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).