[CVE-2026-80990][LOW] net: thunderbolt: Release the Rx HopID that was handed out on mismatch

[CVE-2026-80990][LOW] net: thunderbolt: Release the Rx HopID that was handed out on mismatch

[AL-KERNEL]

CVE: CVE-2026-80990
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net: thunderbolt: Release the Rx HopID that was handed out on mismatch
Commit: 9eac1817bfc5fa76e3a2d1b8fd824cc6ef5a9ab0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9eac1817bfc5fa76e3a2d1b8fd824cc6ef5a9ab0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80990
Analysis date: Sat, 12 Sep 2026 04:50:11 -0400
ActionableScore: 2
ActionableScore lower bound: 1
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-2026-80990 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80990

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-2026-80990	LOW	https://www.kernelcve.org/list/?q=CVE-2026-80990 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';*CWE-772;CWE-404;**CWE-400;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.2';DESCR 'Thunderbolt networking can leak an Rx HopID when tbnet_connected_work requests the peers transmit path and tb_xdomain_alloc_in_hopid returns a different free ID instead of the requested one. The old path treats the mismatch as a failure but leaves the returned HopID allocated for the lifetime of the XDomain connection, which can exhaust available identifiers and prevent later tunnel or tbnet setup. For the CVSS the PR:N is used for the paranoid score because a malicious Thunderbolt or USB4 peer can trigger the condition without an account on the victim system, although physical or local link access to the Thunderbolt domain is required. The issue is not Internet reachable and is limited to systems where Thunderbolt networking or XDomain connectivity is enabled. Impact is denial of service through resource exhaustion only. No memory corruption, information disclosure, or privilege escalation primitive is indicated by the code change.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	SIMPLEFIX NETWORK DMAorINTERRUPT  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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

ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1. No floor or cap applied.
* Raw paranoid score: 2
* Paranoid score: 2. No floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Conservative signals:

* +1 Concrete persistent kernel resource/reference leak. `tb_xdomain_alloc_in_hopid()` may allocate a HopID different from the requested one, and the old error path returned without releasing that allocated ID.
* +0 Reliable kernel crash / strong DoS not awarded. The patch shows a leaked identifier/resource, not a kernel panic or host-wide fatal fault.
* +0 Confidentiality and integrity not awarded. No information disclosure, memory corruption, authorization bypass, or write primitive is established.
* +0 UAF and repeated release/refcount not awarded. There is no stale object dereference, double put, double free, or refcount mutation through a dangling reference.
* +0 Remote network reachability not awarded. Thunderbolt networking is not Internet/network-packet reachable in the usual sense and requires Thunderbolt/USB4 XDomain connectivity.

Paranoid additional signal:

* +1 Sustained local-link resource exhaustion concern. A malicious or faulty Thunderbolt/USB4 XDomain peer may repeatedly drive mismatch situations and exhaust available HopIDs for the connection, preventing later tunnel or tbnet setup.

Non-awarded material signals:

* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Real UAF not demonstrated.
* Concrete repeated release/refcount mutation not demonstrated.
* Security-boundary bypass not demonstrated.
* Privilege escalation not demonstrated.
* Extra availability not awarded for the same resource exhaustion beyond the paranoid sustained exhaustion point.

3. Reachability analysis

The likely trigger is a Thunderbolt networking/XDomain peer causing `tbnet_connected_work()` to request a specific Rx HopID while `tb_xdomain_alloc_in_hopid()` returns another free ID above it. The attacker model is a malicious, faulty, or attacker-controlled Thunderbolt/USB4 peer on the local physical/link-adjacent Thunderbolt domain.

Host administrator privileges on the victim are not required for a pure malicious-peer model, so `HostAdminRequired=NO`. This is not namespace-scoped, and Linux user/network namespaces are not relevant to the complete trigger. Practical exposure depends on Thunderbolt/USB4 hardware, Thunderbolt security/authorization policy, and whether Thunderbolt networking or XDomain connectivity is enabled. There is no ordinary Internet remote vector and no packet-only trigger from a normal IP network.

No race is required by the patch. The condition is an ordered allocation mismatch and missing release path.

4. Primitive and severity interpretation

The exact primitive is a persistent kernel resource/reference leak of an Rx HopID. This is not memory corruption and not a UAF. The leaked HopID remains allocated for the lifetime of the XDomain connection with no remaining owner, which can cause local Thunderbolt networking or DMA tunnel setup failures if identifiers are exhausted.

Primitive class is `CLASS_C` because the demonstrated behavior is resource exhaustion / DoS without an independently useful corruption, lifetime, ownership, or authorization primitive. The demonstrated consequence is denial of service for Thunderbolt networking or tunnel setup. Speculative consequences beyond DoS are not supported by the patch.

`ImportantCandidate=NO` because there is no memory corruption, no concrete UAF, no repeated lifetime/refcount mutation, no controlled overwrite, no information disclosure, and no security-boundary bypass. `AutoDowngradeAllowed=YES` because this is a constrained resource leak with low practical exposure and no unresolved Important-grade primitive.

5. One-sentence report phrase

Thunderbolt networking can leak an Rx HopID when allocation returns a different ID than requested, allowing a local Thunderbolt or USB4 XDomain peer to cause resource exhaustion and tbnet setup failure without evidence of memory corruption or privilege escalation.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: the patch establishes a concrete resource leak only, with no UAF, no memory corruption, no authorization bypass, and no plausible Important-grade primitive.

7. Call-site confidence

Call-site confidence: high

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

Patch: net: thunderbolt: Release the Rx HopID that was handed out on mismatch
Commit: 9eac1817bfc5fa76e3a2d1b8fd824cc6ef5a9ab0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9eac1817bfc5fa76e3a2d1b8fd824cc6ef5a9ab0

Commit description:

tb_xdomain_alloc_in_hopid() passes the wanted HopID to ida_alloc_range()
as the lower bound, so a taken id is not an error there: the allocator
returns the next free one above it. tbnet_connected_work() asks for the
peer's transmit path, treats any other id as a failure and returns
without releasing what it got, so that allocation stays live for the rest
of the XDomain connection with nothing left holding a reference to it.

Release the id when it is not the one we asked for, the same way the
error unwind at the end of the function releases the expected one.

Fixes: 180b068 ("thunderbolt: Allow multiple DMA tunnels over a single XDomain connection")
Cc: stable@vger.kernel.org
Signed-off-by: Fan Ye <fy15309206903@gmail.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260811-b4-tbnet-hopid-v3-1-9e75d1b51331@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/thunderbolt/main.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=9eac1817bfc5fa76e3a2d1b8fd824cc6ef5a9ab0

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

The original Linux kernel CVE announcement for CVE-2026-80990 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80990

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:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.2

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: 1
  Paranoid ActionableScore: 2

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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).