[CVE-2026-80989][MODERATE 7.0] net: thunderbolt: Mark the connection down when bringing it up fails

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-80989
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: net: thunderbolt: Mark the connection down when bringing it up fails
Commit: ed1d6e3d735e7b03f43a02f4306c89eb7663da14
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ed1d6e3d735e7b03f43a02f4306c89eb7663da14
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80989
Analysis date: Fri, 11 Sep 2026 21:25:18 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-80989 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80989

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.

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AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-80989	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80989 CHECK WITH IMPACT FROM ORIG NN LOW	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:L/A:H';CWE-404;*CWE-664;CWE-703;Other CVSS 'AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H';BEST CVSS score: '5.9';DESCR 'Thunderbolt networking can leave login_sent set after tbnet_connected_work() fails while bringing a connection up. A later teardown can then repeat cleanup of state that was already unwound, stop rings that are already stopped, and trigger a dev_WARN that can become fatal when panic_on_warn is enabled. The HopID mismatch path can also release net remote_transmit_path even though this connection did not own that id, which may disrupt another active Thunderbolt networking path. For the CVSS the PR:N is used in the paranoid score because a malicious or faulty Thunderbolt peer does not need a local account on the victim once it can interact with the Thunderbolt networking link. The issue is adjacent reachable rather than Internet reachable. Impact is denial of service, with limited integrity risk from incorrect release of a path id owned by another connection.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4)	YES	LOCK SIMPLEFIX NETWORK LOG KPANIC 	NO	NO	checked

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

ActionableScore=4
ActionableScoreLower=3
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 4
* Paranoid score: 4
* Final recommended bucket: **Borderline / manual review recommended**::

No floor or cap changed the conservative or paranoid score.

2. Signal breakdown

Positive signals:

* +1 Adjacent Thunderbolt peer influence. The vulnerable state can be influenced by a Thunderbolt networking peer during connection setup failure, but this is adjacent or cable level exposure, not Internet remote exposure.
* +1 Active resource ownership or lifetime state mismatch. `login_sent` remains true after setup has already been unwound, so later teardown repeats cleanup on state that should no longer be treated as established.
* +1 Conditional strong DoS. Repeated teardown can stop already stopped rings and trigger `dev_WARN()`, which is fatal when `panic_on_warn` is enabled.
* +1 Paranoid only, limited integrity or resource ownership concern. The HopID mismatch path may release `net->remote_transmit_path` even though this connection never owned that id, potentially disrupting another active Thunderbolt networking path.

Non-awarded or limited signals:

* RealUAF not awarded. The patch does not establish a heap use-after-free or stale post-free object dereference.
* Concrete repeated release or refcount signal not awarded. The released HopID is a resource identifier, not a visible object reference whose first release can free an object followed by a second refcount mutation on the exact same dangling object.
* Strong LPE or strong exploitation leverage not awarded. There is no controlled reclaim, arbitrary write, callback control, credential impact, or demonstrated privilege escalation.
* Direct remote network reachability not awarded. Thunderbolt networking is adjacent or local-link style exposure and requires Thunderbolt peer interaction.
* Extra availability not awarded beyond the WARN or panic path. The same crash condition is not double-counted.
* Confidentiality not awarded. No disclosure path is shown.
* Full high integrity impact not awarded. The HopID release issue is a limited resource ownership concern, not demonstrated arbitrary modification of protected kernel state.

Negative signals:

* No host-admin privilege penalty applied. The supplied evidence supports a malicious or faulty Thunderbolt peer model rather than requiring a local host administrator account on the victim.
* No race penalty applied. The issue is primarily stale connection state after ordered failure paths, not a narrow timing race.
* No rare-hardware penalty applied. Thunderbolt is hardware-specific and adjacent, but the evidence does not justify treating it as rare or host-admin-only.

3. Reachability analysis

The plausible attacker is a malicious, faulty, or compromised Thunderbolt networking peer interacting with the victim over a Thunderbolt link. This is not Internet remote and should be treated as adjacent reachability.

The complete trigger appears to require Thunderbolt networking to be active or available and a connection setup failure path in `tbnet_connected_work()`. Once the peer can interact with the Thunderbolt networking link, no local user account on the victim is required for the peer-side trigger, so `HostAdminRequired=NO`.

This is not a namespace-scoped privilege case. Network namespaces and container capabilities are not material to the supplied patch, so `NamespaceScopedPrivilege=NO`.

Prior setup may be needed in practice because Thunderbolt networking must be enabled and the peer must be connected or authorized according to platform policy. That is an environmental exposure condition, not evidence that exploitation requires host-admin-equivalent privileges by the attacker.

No hard race is established. The failure path leaves `login_sent` set, and later teardown observes stale state.

4. Primitive and severity interpretation

The exact primitive is a connection-state lifetime or ownership mismatch. Failed connection setup unwinds resources but leaves `login_sent` true, so subsequent teardown treats the connection as established and performs cleanup again.

This is not a demonstrated memory UAF. It is also not a concrete repeated refcount mutation on a freed object. The most security-relevant behavior is repeated teardown of already unwound state and incorrect release of a HopID that may belong to another connection.

The object state is active structured driver/networking state rather than fixed passive metadata, but the demonstrated consequences are constrained: WARN or panic under `panic_on_warn`, and possible disruption of another Thunderbolt networking path.

Primitive class is `CLASS_B` because an active resource ownership and lifetime-state violation is established. It is not `CLASS_A` because there is no controlled corruption, arbitrary read/write, controlled reclaim, security-boundary bypass, or demonstrated LPE.

`ImportantCandidate=NO` because the unresolved leverage does not rise to an Important-preserving kernel corruption primitive. `ManualReview=RECOMMENDED` because adjacent peer reachability plus wrong release of another path id deserves human validation. `AutoDowngradeAllowed=YES` because the demonstrated impact remains constrained DoS and limited resource disruption without a memory corruption or privilege-escalation primitive.

Likely operational severity is Borderline to Actionable Moderate depending on whether Thunderbolt networking is enabled and whether `panic_on_warn` is used.

5. One-sentence report phrase

Thunderbolt networking can leave `login_sent` set after connection setup failure, causing later teardown to repeat cleanup, trigger a fatal WARN under `panic_on_warn`, and possibly release a HopID owned by another connection.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: adjacent Thunderbolt peer reachability and the incorrect release of a resource id owned by another connection make this more than a pure harmless WARN, but the patch does not establish UAF, arbitrary corruption, information disclosure, or privilege escalation.

7. Call-site confidence

Call-site confidence: medium

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

Patch: net: thunderbolt: Mark the connection down when bringing it up fails
Commit: ed1d6e3d735e7b03f43a02f4306c89eb7663da14
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ed1d6e3d735e7b03f43a02f4306c89eb7663da14

Commit description:

Every failure path in tbnet_connected_work() undoes its own work and
returns without clearing login_sent, so the connection still looks
established. The next tbnet_tear_down() therefore takes its main branch
and repeats a teardown that already happened: it stops rings that are
already stopped, which is a dev_WARN() and fatal under panic_on_warn,
and it releases net->remote_transmit_path even on the HopID mismatch
path, where this connection never owned that id, silently freeing one
that someone else is still using.

Clear login_sent on those paths. That is enough for tbnet_tear_down() to
leave the unwound state alone, and login_received has to stay set: it
records that the peer has logged in and carries the transmit path it gave
us, which nothing on this side can make the peer send again. Two things
change beyond keeping the teardown out of the way: the logout request in
that block is no longer sent, and the peer's next login request now
re-queues our login work rather than connected_work, giving the
connection a fresh login instead of a retry on stale state.

Fixes: e69b6c0 ("net: Add support for networking over Thunderbolt cable")
Cc: <stable@vger.kernel.org> # 5.13+
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-v3-2-9e75d1b51331@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=ed1d6e3d735e7b03f43a02f4306c89eb7663da14

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

The original Linux kernel CVE announcement for CVE-2026-80989 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80989

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:R/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
  The Best / paranoid CVSS score: 5.9

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