* [CVE-2026-99010][MODERATE REGULAR] Bluetooth: RFCOMM: free the skb when the DLC has no owner
@ 2026-10-27 1:22 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-27 1:22 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-99010
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Bluetooth: RFCOMM: free the skb when the DLC has no owner
Commit: a54ce160e3ef7e50ec94e0ac4131c3d0f9f739b9
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a54ce160e3ef7e50ec94e0ac4131c3d0f9f739b9
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99010
Analysis date: Mon, 26 Oct 2026 21:22:58 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
An adjacent RFCOMM peer can sustain an skb leak during the ownerless connected-DLC window, potentially causing kernel memory pressure or OOM.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99010 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99010
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: YES
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-99010 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99010 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE RESULT=DIFF (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';*CWE-401;**CWE-400;*CWE-772;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.3';DESCR 'An RFCOMM socket callback returned without freeing an skb when a connected DLC no longer had an owner. A nearby Bluetooth peer with an established RFCOMM connection can send data during the interval after socket destruction and leak one skb for every accepted frame. Continued credit grants allow the peer to sustain the leak and may eventually cause kernel memory pressure or OOM. For the CVSS the PR:N value is used because the peer does not require privileges on the target, although Bluetooth adjacency, an established DLC, and the ownerless lifecycle window are required. There is no evidence of UAF, OOB access, information disclosure, or an arbitrary write primitive. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.3 and the production ActionableScore returned 4 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were KP and FD specialist checks stage MODERATE_KPANIC to MODERATE because KP specialist did not establish a qualifying panic. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP and V41_INHERITED_KPANIC_PROMOTION_BLOCKED and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 3.1 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) MAYBE REMOTE LEAK NETWORK SKB HARDWARE LINUS MEMORY DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP V41_INHERITED_KPANIC_PROMOTION_BLOCKED MANUAL_REVIEW_REQUIRED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=4
ActionableScoreLower=3
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: 3.
* Conservative score: 3; no floor or cap applied.
* Raw paranoid score: 4.
* Paranoid score: 4; no floor or cap applied.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
* +2 Remote/network reachability: an adjacent Bluetooth peer with an established RFCOMM DLC can send the frames reaching the leaking callback without target-host privileges.
* +1 Concrete persistent kernel resource leak: `rfcomm_sk_data_ready()` loses ownership of each skb when `d->owner == NULL`; the patch adds the missing `kfree_skb()`.
* Paranoid +1 Strong DoS: continued credit grants permit sustained accumulation, making severe memory pressure or OOM technically credible, though no observed panic or guaranteed host failure is shown.
* No timing penalty: the ownerless lifecycle state is required, but the leak continues once reached; no narrow or unreliable race is established.
* No extra availability point: any OOM/crash is the same potential DoS consequence.
* No UAF, OOB access, attacker-directed overwrite, disclosure, authorization bypass, or protected-resource impact is shown.
* NEW52 B5-R and NEW53 B3-PENDING do not apply: there is no write outside an allocation or write to shared backing.
3. Reachability analysis
The attacker is a nearby Bluetooth peer participating in an established RFCOMM connection. No host UID 0, host capability, namespace capability, or separate privileged retry setup is shown as necessary for sending frames. The victim must enter the interval after socket destruction while the connected DLC remains in the session. The patch evidence indicates that credit replenishment lets the peer sustain the leak rather than relying on a one-shot race.
4. Primitive and severity reading
The exact defect is a persistent skb ownership leak, not stale-object use or memory corruption. Its supported effect is accumulating kernel memory consumption; OOM or host-wide failure remains plausible rather than demonstrated. This is CLASS_C availability behavior, with no Important-preserving primitive. Auto-downgrade remains allowed because no unresolved corruption or security-boundary mechanism exists.
5. One-sentence report phrase
An adjacent RFCOMM peer can sustain an skb leak during the ownerless connected-DLC window, potentially causing kernel memory pressure or OOM.
6. Manual review advice
MANUAL CHECK RECOMMENDED
Confirm practical duration and repeatability of the ownerless DLC window and whether product memory controls turn sustained leakage into host-wide OOM.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: Bluetooth: RFCOMM: free the skb when the DLC has no owner
Commit: a54ce160e3ef7e50ec94e0ac4131c3d0f9f739b9
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a54ce160e3ef7e50ec94e0ac4131c3d0f9f739b9
Commit description:
rfcomm_recv_data() hands the skb to d->data_ready() and returns 0
without freeing it, so the callback owns the skb from that point on.
The tty implementation frees it when the DLC has been detached from its
device:
static void rfcomm_dev_data_ready(struct rfcomm_dlc *dlc,
struct sk_buff *skb)
{
struct rfcomm_dev *dev = dlc->owner;
if (!dev) {
kfree_skb(skb);
return;
}
The socket implementation returns without freeing it, and the skb is
leaked.
A connected DLC can have no owner: rfcomm_sock_destruct() clears
d->owner, while the DLC itself stays on the session until it is closed.
Data frames that arrive in that window still find d->state ==
BT_CONNECTED in rfcomm_recv_data() and are handed to the callback, one
leaked skb each.
The leak does not stop on its own either. The remote runs out of
credits only once RFCOMM_RX_THROTTLED is set, and for a socket the only
place that sets it is rfcomm_sk_data_ready() itself, below the return.
rfcomm_process_dlcs() keeps granting credits, so the remote keeps
sending and the leak keeps growing.
Free the skb, as the tty side does.
Fixes: 1da177e ("Linux-2.6.12-rc2")
Reported-by: Mikhail Gavrilov <[email protected]>
Closes: https://lore.kernel.org/linux-bluetooth/CABXGCsPe5wykd8Aj-hm+SJ7SGQyb8yoGNnx3XDpPmBathj+EGg@mail.gmail.com/
Cc: [email protected]
Signed-off-by: Maxim Skokov <[email protected]>
Assisted-by: Claude:claude-opus-5
Reviewed-by: Mikhail Gavrilov <[email protected]>
Signed-off-by: Luiz Augusto von Dentz <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
net/bluetooth/rfcomm/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=a54ce160e3ef7e50ec94e0ac4131c3d0f9f739b9
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99010 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99010
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:N/I:N/A:L
The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 5.3
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: 3
Paranoid ActionableScore: 4
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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