* [CVE-2026-80760][MODERATE 7.0] Bluetooth: MGMT: reject HCI_CMD_SYNC params_len above 255
@ 2026-09-04 20:12 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-04 20:12 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-80760
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Bluetooth: MGMT: reject HCI_CMD_SYNC params_len above 255
Commit: b7d9edcf9fe6e9ec3a2e80ef9e8d44ef9b4f2894
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b7d9edcf9fe6e9ec3a2e80ef9e8d44ef9b4f2894
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80760
Analysis date: Fri, 04 Sep 2026 16:12:58 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: NO
Summary:
Bluetooth MGMT HCI_CMD_SYNC allowed params_len above 255, causing HCI header length truncation and possible controller command stream desynchronization, with local management privileges typically required and impact mainly DoS or unintended controller behavior.
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ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80760 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80760
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: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-80760 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-80760 CHECK WITH IMPACT FROM ORIG NN LOW 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:L/A:H';CWE-197;*CWE-20;CWE-130;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '5.3';DESCR 'Bluetooth MGMT HCI_CMD_SYNC accepted a params_len value that fits the management message but does not fit the u8 parameter length field in the HCI command header. A local actor with access to the Bluetooth management interface could set params_len to more than 255, causing the header length to be truncated while the full parameter bytes are still appended to the outgoing frame. On length framed transports such as H:4, the controller may treat the trailing bytes as the start of another HCI packet, causing command stream desynchronization, unintended controller behavior, or denial of service. For the CVSS the PR:L is used for the paranoid score because reduced capability root, a service account, or delegated Bluetooth management access may be enough in some deployments. The issue is not directly network reachable from a remote Bluetooth peer and does not show a kernel memory corruption primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) YES REMOTE NETWORK PACKET DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH YES NO checked
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ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
ActionableScoreLower=3
## 1. ActionableScore
Conservative score: 3
Paranoid score: 5
Final recommended bucket: **Actionable Moderate at minimum**::
## 2. Signal breakdown
Conservative signals:
- Strong attacker-influenced semantic reinterpretation primitive: +2. The same attacker-controlled bytes are accepted as MGMT command parameters using a 16-bit length, but later encoded into an HCI command header with an 8-bit length, causing trailing bytes to be interpreted differently by the controller transport.
- Firmware-mediated external influence: +1. The malformed frame is handed to the Bluetooth controller or transport, and the practical impact depends on controller or H:4 framing behavior.
- Integrity impact plausible: +1. Trailing bytes may be treated as a following HCI packet, which can cause unintended controller command stream behavior.
- Availability impact realistic: +1. Desynchronization of the HCI command stream can plausibly disrupt the Bluetooth controller or stack.
- Requires admin/root/CAP_NET_ADMIN in typical deployments: -2. Bluetooth MGMT operations are normally local privileged management operations.
Paranoid additional signal:
- Additional semantic reinterpretation concern: +1. The reinterpreted trailing bytes may represent active HCI packets or controller operations, not just passive malformed metadata.
## 3. Reachability analysis
The trigger is local through the Bluetooth MGMT interface, not from a remote Bluetooth peer directly. Typical exploitation requires CAP_NET_ADMIN or equivalent Bluetooth management access, so the conservative interpretation treats it as privileged local. In some deployments, a reduced-capability service account, container root with delegated device access, or a Bluetooth management daemon interface could make PR:L a defensible paranoid interpretation. The issue requires a Bluetooth controller and a transport where trailing bytes can be parsed as a subsequent packet, such as H:4.
## 4. Severity interpretation
This is not kernel memory corruption, UAF, OOB write, or direct privilege escalation. It is stronger than ordinary input validation because it creates a validation-to-use semantic mismatch where attacker-controlled bytes can be consumed as active HCI transport data. Realistic impact is controller or Bluetooth stack DoS and possible unintended controller behavior. This fits Actionable Moderate rather than Important, but should not be auto-closed because controller-specific behavior may materially change impact.
## 5. One-sentence report phrase
Bluetooth MGMT HCI_CMD_SYNC allowed params_len above 255, causing HCI header length truncation and possible controller command stream desynchronization, with local management privileges typically required and impact mainly DoS or unintended controller behavior.
## 6. Manual review recommendation
MANUAL CHECK RECOMMENDED. The bug is not a kernel memory corruption primitive, but the HCI transport semantic reinterpretation can be controller-specific and may cause effects beyond a simple validation failure.
YES REQUIRES MANUAL CHECK
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: Bluetooth: MGMT: reject HCI_CMD_SYNC params_len above 255
Commit: b7d9edcf9fe6e9ec3a2e80ef9e8d44ef9b4f2894
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b7d9edcf9fe6e9ec3a2e80ef9e8d44ef9b4f2894
Commit description:
mgmt_hci_cmd_sync() checks that the message length agrees with params_len
but puts no upper bound on it. params_len is __le16 while the parameter
length in the HCI command header is a u8:
struct hci_command_hdr {
__le16 opcode;
__u8 plen;
} __packed;
hci_cmd_sync_alloc() assigns one to the other:
hdr->plen = plen;
if (plen)
skb_put_data(skb, param, plen);
so a params_len of 256 leaves plen at 0 while all 256 bytes are still
appended. The frame handed to the driver then declares no parameters and
carries 256 of them. On a length framed transport such as H:4 the
controller takes the trailing bytes as the start of the next packet.
The mgmt socket MTU is HCI_MAX_FRAME_SIZE, so params_len can reach about
1KB this way. Commit 03f1700 ("Bluetooth: MGMT: reject malformed
HCI_CMD_SYNC commands") only made params_len agree with the message
length, a value that fits the message but not the header field is still
accepted.
Reject params_len that does not fit the header field.
Fixes: 827af47 ("Bluetooth: MGMT: Add initial implementation of MGMT_OP_HCI_CMD_SYNC")
Cc: [email protected]
Signed-off-by: Ali Ahmet Memis <[email protected]>
Signed-off-by: Luiz Augusto von Dentz <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
net/bluetooth/mgmt.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=b7d9edcf9fe6e9ec3a2e80ef9e8d44ef9b4f2894
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80760 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80760
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:H/UI:N/S:U/C:N/I:L/A:L
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/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: 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: NO
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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