* [CVE-2026-93209][LOW] Revert "Bluetooth: hci_sync: Fix overwriting request callback" This reverts commit da77c1d which is
@ 2026-09-24 18:20 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-24 18:20 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-93209
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: Revert "Bluetooth: hci_sync: Fix overwriting request callback" This reverts commit da77c1d which is
Commit: 0337fb092873a4146aa854acb554675b49c8f6b5
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0337fb092873a4146aa854acb554675b49c8f6b5
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93209
Analysis date: Thu, 24 Sep 2026 14:20:42 -0400
ActionableScore: 0
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-2026-93209 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93209
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-2026-93209 LOW https://www.kernelcve.org/list/?q=CVE-2026-93209 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:N/I:N/A:L';CWE-252;CWE-703;**CWE-400;BEST CVSS score: '2.5';DESCR 'A Bluetooth HCI synchronous command can time out when skb_clone fails under memory pressure while saving the sent command in hdev req_skb. The firmware can return a successful response, but the missing req_skb prevents the completion callback from waking the waiting task and the request ends with ETIMEDOUT after the timeout period. This can disrupt Bluetooth initialization or command processing and results in limited local availability impact. For the CVSS the PR:L is selected because reliably triggering the condition requires local control of memory pressure and interaction with the local Bluetooth command path. The issue is not shown to be directly network reachable from a remote Bluetooth peer. The patch context does not establish a memory corruption primitive in hci_core, despite an earlier related investigation mentioning a use after free in a separate ttyport failure path.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) YES REMOTE UAF NETWORK SKB LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 YES NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* Final recommended bucket: **Ordinary Moderate**::
No floor or cap applies.
2. Signal breakdown
* +0 No kernel corruption primitive. The patch fixes failure handling for skb_clone under memory pressure. A NULL req_skb prevents completion callback lookup and causes ETIMEDOUT.
* +0 No Real UAF. The commit mentions a previously observed ttyport_close use after free during investigation, but explicitly identifies the req_skb allocation failure as the root cause addressed by this patch. The provided hci_core change does not establish stale use after free.
* +0 No reliable host wide crash or strong DoS. The demonstrated consequence is a ten second timeout and failure of Bluetooth enable or synchronous HCI command processing.
* +0 No remote reachability established. A remote Bluetooth peer does not control the local skb_clone allocation failure in the supplied path.
* +0 No local unprivileged trigger bonus. The evidence does not establish that an ordinary unprivileged user can both reliably create relevant memory pressure and drive the complete affected HCI command path.
* +0 No controlled reclaim, arbitrary write, callback control, information disclosure, integrity impact, authorization bypass, or privilege escalation is demonstrated.
* No privilege penalty applied. Host administrator requirements for the complete Bluetooth control path are not resolved by the supplied context, so HostAdminRequired remains UNKNOWN.
* No race penalty applied. This is an allocation failure and error handling issue, not a demonstrated timing race.
3. Reachability analysis
The failure occurs when hci_send_cmd_sync attempts skb_clone of hdev sent_cmd while the kernel is under memory pressure. The clone can fail, leaving hdev req_skb NULL. The received firmware response is then processed without finding the completion callback, and the waiting synchronous request expires with ETIMEDOUT.
The supplied evidence does not establish a complete attacker controlled path for an ordinary local user, a namespace scoped user, or a remote Bluetooth device. Bluetooth device enable and HCI command processing may be driven by system services or privileged configuration depending on deployment. There is no evidence that all required operations are namespace scoped, so NamespaceScopedPrivilege is UNKNOWN.
No special hardware attack, firmware compromise, boot option, sysctl prerequisite, or remote packet trigger is established. Memory pressure is required, but the patch does not show an attacker controllable resource exhaustion or cross boundary accounting bypass.
4. Primitive and severity interpretation
The exact primitive is an unchecked allocation failure causing an invalid command completion state. The affected object is not used after lifetime end. Instead, hdev req_skb remains NULL because skb_clone failed, so the completion callback cannot be located and the request state remains HCI_REQ_PEND until timeout.
This is not an active structured object UAF, fixed stale storage UAF, repeated release, double free, refcount mutation, or semantic reinterpretation issue. There is no first lifetime operation that may free an object and no second lifetime mutation through a dangling reference.
PrimitiveClass is NONE. The demonstrated consequence is limited availability impact affecting Bluetooth initialization or command processing. A stronger consequence such as kernel crash, memory corruption, information disclosure, integrity loss, or privilege escalation is speculative and unsupported by the patch. ImportantCandidate is NO and AutoDowngradeAllowed is YES because no unresolved kernel corruption or security boundary primitive remains.
5. One-sentence report phrase
A failed skb_clone under memory pressure can leave Bluetooth HCI command completion state unset and cause a synchronous command timeout, disrupting Bluetooth initialization without establishing memory corruption or privilege escalation.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch establishes an allocation failure and timeout handling defect only. It does not establish a UAF, stale lifetime operation, kernel crash, remote trigger, security boundary bypass, or attacker useful memory corruption primitive.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: Revert "Bluetooth: hci_sync: Fix overwriting request callback" This reverts commit da77c1d which is
Commit: 0337fb092873a4146aa854acb554675b49c8f6b5
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0337fb092873a4146aa854acb554675b49c8f6b5
Commit description:
It is reported to cause regressions in the 6.1.y tree, so revert it for
now.
Link: https://lore.kernel.org/all/CADRbXaDqx6S+7tzdDPPEpRu9eDLrHQkqoWTTGfKJSRxY=hT5MQ@mail.gmail.com/
Reported-by: Jeremy Lainé <[email protected]>
Cc: Salvatore Bonaccorso <[email protected]>
Cc: Mike <[email protected]>
Cc: Marcel Holtmann <[email protected]>
Cc: Johan Hedberg <[email protected]>
Cc: Paul Menzel <[email protected]>
Cc: Pauli Virtanen <[email protected]>
Cc: Luiz Augusto von Dentz <[email protected]>
Cc: Sasha Levin <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
include/net/bluetooth/hci_core.h
net/bluetooth/hci_conn.c
net/bluetooth/hci_core.c
net/bluetooth/hci_event.c
net/bluetooth/hci_sync.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=0337fb092873a4146aa854acb554675b49c8f6b5
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-93209 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93209
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:L/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS score: 2.5
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: 0
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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