* [CVE-2026-90093][MODERATE 7.0] Bluetooth: L2CAP: access chan->conn safely in get/setsockopt [ Upstream
@ 2026-09-18 13:00 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-18 13:00 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-90093
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: Bluetooth: L2CAP: access chan->conn safely in get/setsockopt [ Upstream
Commit: f49321c85785178214fd67f2e9b4b73d6363783b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f49321c85785178214fd67f2e9b4b73d6363783b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90093
Analysis date: Fri, 18 Sep 2026 09:00:40 -0400
ActionableScore: 5
ActionableScore lower bound: 4
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-2026-90093 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90093
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-2026-90093 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-90093 CHECK WITH IMPACT FROM ORIG NN IMPORTANT Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A race in the Bluetooth L2CAP socket option paths can access chan conn after the associated hci_conn has already been deleted. The retained chan conn reference can remain non NULL while conn hcon and fields such as hdev are no longer valid, resulting in a KASAN detected use after free access and a possible kernel crash. For the CVSS the PR:L reflects that a local user or process must normally create or operate an L2CAP socket and invoke getsockopt or setsockopt during connection teardown. AC:H is appropriate because reliable triggering depends on winning a timing window between socket option processing and connection deletion. A remote Bluetooth peer may influence disconnect timing, but the peer alone cannot directly issue the required local socket option calls, so the vulnerability is not classified as directly network reachable. Impact is at least local denial of service through a kernel crash. In the paranoid interpretation the stale object access may also cause limited confidentiality or integrity impact if freed memory is reused, but no reliable arbitrary write or privilege escalation primitive is established.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) SKIP CVE-2026-90093 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE REMOTE DANGER RACE UAF NETWORK KERNEL_PANIC_PLUS_UAF SYZBOT KPANIC KPANIC LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
1. ActionableScore
* Raw conservative score: 4
* Conservative score: 4
* Raw paranoid score: 5
* Paranoid score: 5
* No floor or cap changed either score.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
Conservative positive signals:
* +2 Real UAF and lifetime violation. `chan->conn` remains non-NULL after the associated `hci_conn` and its `hcon` state are deleted. Socket-option paths subsequently dereference that stale state.
* +1 Reliable kernel crash. The commit reports a KASAN crash while `l2cap_sock_setsockopt()` accesses `conn->hcon->hdev`.
* +1 Local unprivileged trigger. Ordinary local processes can operate non-raw L2CAP sockets and invoke the affected `getsockopt()` or `setsockopt()` operations without host-admin-equivalent privilege.
Paranoid-only signal:
* +1 Attacker-influenced lifetime transition. A local process controlling an L2CAP socket can repeatedly invoke socket-option operations around connection teardown. This provides a defensible opportunity to exercise the stale active object beyond a one-time passive cleanup path.
Non-awarded signals:
* Controlled reclaim or attacker-shaped replacement contents are not demonstrated.
* Arbitrary or directed kernel write is not demonstrated.
* Structured stale-object leverage is not separately awarded. The stale paths consume active fields and invoke helpers, but meaningful control over reclaimed contents is not established.
* Weak LPE is not awarded merely because this is a UAF.
* Confidentiality and integrity points are not awarded merely because reused memory could theoretically affect returned security or connection fields.
* Direct remote reachability is not established. A Bluetooth peer may influence disconnection timing but cannot independently issue the required local socket-option calls.
* No extra Availability point is awarded because the KASAN fault and kernel crash are the same consequence.
* No race penalty is applied. The evidence does not establish a one-shot, externally uncontrollable, or exceptionally narrow race.
* No hardware penalty is applied. A Bluetooth controller or emulated HCI path is needed, but the evidence does not establish rare or physical-only hardware.
* No concrete repeated release or refcount mutation exists. The stale operations dereference fields and pass `hcon` to helpers rather than performing a second `put`, `free`, or refcount decrement on the exact dangling reference.
* FLOOR 5 is not applied to the conservative score. The paranoid score reaches 5 through attacker-influenced repeated exercise of the active lifetime transition, not through a hidden floor.
3. Reachability analysis
The evaluated attacker is a local user process that can create or operate an L2CAP socket, establish or obtain an L2CAP connection, and invoke the affected socket options while the underlying HCI connection is being deleted. Non-raw L2CAP socket use is below host-admin privilege, so `HostAdminRequired=NO`.
No namespace capability is needed for the basic socket-operation path, and Bluetooth HCI ownership is not established here as an attacker-created user-namespace capability. Therefore `NamespaceScopedPrivilege=NO`.
A usable Bluetooth or emulated HCI connection is a prerequisite, but no separate host-admin actor is shown as necessary once the interface is available. A remote Bluetooth peer can contribute to link teardown or timing but cannot complete the trigger without a cooperating local process.
The bug is a race, but repeated socket-option calls and repeated connection lifecycle operations are plausible. The supplied evidence does not justify treating the timing as a genuinely hard one-shot race.
4. Primitive and severity interpretation
The exact primitive is a stale post-lifetime dereference of active HCI connection state. `l2cap_chan::conn` remains referenced and non-NULL, but its associated `hcon` can already be invalid after `l2cap_conn_del()` begins deletion. The affected paths read fields such as `handle`, `dev_class`, `sec_level`, `enc_key_size`, and `hdev`, and pass stale state into helpers including `hci_conn_get_phy()`, `hci_conn_set_phy()`, and `smp_conn_security()`.
This is an active structured-object UAF rather than fixed stale storage. It is also broader than a destructor-only fault because ordinary `getsockopt()` and `setsockopt()` paths consume the stale state and may invoke nontrivial Bluetooth security or PHY operations.
There is no concrete second release or refcount mutation on the dangling object. The demonstrated consequence is a KASAN-detected invalid access and kernel crash. Controlled reclaim, arbitrary read or write, callback control, and privilege escalation remain unproven.
`PrimitiveClass=CLASS_B` is appropriate because a real active-object lifetime violation exists, but no Class A exploitation primitive is established. `ImportantCandidate=YES` reflects unresolved leverage from passing stale HCI state into active helper operations, not an assertion that LPE is proven. `AutoDowngradeAllowed=NO` because automatically reducing this to an ordinary crash would discard a below-host-admin active-object UAF whose post-reuse behavior requires inspection.
The practical lower assessment is Actionable Moderate. An Important classification would require evidence of controllable object reuse, attacker-shaped stale fields, unauthorized state changes, disclosure, directed writes, or privilege escalation.
5. One-sentence report phrase
A local user operating an L2CAP socket can race connection teardown with socket-option processing and dereference deleted HCI connection state, causing a kernel crash while leaving the exploitation value of stale state passed into active Bluetooth helpers unresolved.
6. Manual review recommendation
MANUAL CHECK REQUIRED
Review allocator reuse for `hci_conn` and related objects, plus the behavior of `smp_conn_security()`, `hci_conn_set_phy()`, and other helpers when supplied a stale or replaced `hcon`, to determine whether the primitive extends beyond crash-only behavior.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: Bluetooth: L2CAP: access chan->conn safely in get/setsockopt [ Upstream
Commit: f49321c85785178214fd67f2e9b4b73d6363783b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f49321c85785178214fd67f2e9b4b73d6363783b
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=f49321c85785178214fd67f2e9b4b73d6363783b
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90093 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90093
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:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
The Best / paranoid CVSS score: 5.8
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: 4
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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