* [CVE-2026-97508][MODERATE REGULAR] thunderbolt: Set tb->root_switch to NULL when domain is stopped [ Upstream
@ 2026-09-24 21:29 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-24 21:29 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-97508
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: thunderbolt: Set tb->root_switch to NULL when domain is stopped [ Upstream
Commit: f06e9fbae78a51832211b4495a19412c7d49ecb4
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f06e9fbae78a51832211b4495a19412c7d49ecb4
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97508
Analysis date: Thu, 24 Sep 2026 17:29:22 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97508 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97508
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-2026-97508 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-97508 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:L/I:L/A:H';*CWE-416;CWE-362;**CWE-476;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'A race exists between Thunderbolt XDomain request handling and Thunderbolt domain shutdown. tb_xdp_handle_request can retain a pointer to root_switch uuid after releasing tb lock, while tb_stop can remove and free the root switch. A connected remote Thunderbolt peer may issue XDomain requests while the local domain is being stopped, causing a use after free and potentially a kernel crash. For the CVSS the PR:N value is used because the attacker only needs access to a connected Thunderbolt fabric and does not require a local user account on the victim. The attack vector is adjacent AV:A rather than network reachable because it requires a physical Thunderbolt connection or access to the same Thunderbolt domain. Impact is at least denial of service through a kernel crash. In the paranoid case limited confidentiality and integrity impact cannot be excluded because the bug is a kernel use after free, but a privilege escalation primitive is not demonstrated. YES REQUIRES MANUAL CHECK.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) YES INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=3
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 3
* Paranoid score: 3
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
* +2 Real UAF or active lifetime violation. `tb_xdp_handle_request()` obtains a direct pointer to `tb->root_switch->uuid` while holding `tb->lock`, releases the lock, and subsequently uses the pointer. Concurrent `tb_stop()` removes the root switch, so the pointer can refer to freed root-switch storage.
* +1 Realistic kernel crash or DoS. Dereferencing or copying from the stale UUID pointer can fault if the former root-switch allocation has been freed or unmapped.
* No direct remote network reachability bonus. The peer communicates over a Thunderbolt fabric, which is an adjacent physical interconnect, not an IP network service.
* No hard-race penalty. The patch establishes concurrent request handling and shutdown, but does not establish that the timing window is exceptionally narrow or practically unreproducible.
* No hardware-only penalty. Thunderbolt is hardware-dependent, but the supplied evidence does not prove an unusually rare device configuration beyond the required connected Thunderbolt peer.
* Controlled reclaim is not demonstrated.
* Arbitrary write is not demonstrated.
* Structured stale-object leverage is not awarded. The demonstrated stale use is a shallow read of the embedded UUID and related root-switch lookup during shutdown, not consumption of attacker-controlled reclaimed object fields.
* Weak LPE concern is not awarded. A kernel UAF exists, but there is no demonstrated replacement, callback, pointer redirection, refcount mutation, disclosure, or privilege-boundary bypass.
* Extra Availability impact is not awarded because the potential kernel crash is already counted.
* Confidentiality and integrity impact are not awarded. The patch does not establish that stale UUID data is disclosed or that attacker-controlled data is written through the stale reference.
* No concrete repeated release or refcount mutation exists. The patch copies a UUID and clears a pointer. It does not show a second put, release, free, or refcount operation on the same dangling object.
3. Reachability analysis
A connected Thunderbolt XDomain peer can send a request that reaches `tb_xdp_handle_request()`. This does not require a local user account or host administrative privilege merely to submit the request.
However, the complete trigger requires concurrent Thunderbolt-domain shutdown. The supplied patch does not establish whether the remote peer can independently and reliably initiate the relevant stop sequence, for example through disconnect or link-state behavior, or whether shutdown is initiated by host lifecycle activity such as device removal, suspend, or driver teardown. Therefore, `HostAdminRequired=UNKNOWN` is appropriate for the complete trigger rather than assuming either host administrator control or fully attacker-controlled shutdown.
No relevant namespace-scoped capability is involved. The attack surface is an adjacent Thunderbolt fabric and requires a physically connected or otherwise authorized Thunderbolt peer. It is not directly reachable from an ordinary network connection.
Race repeatability is unresolved. A connected peer can likely submit repeated XDomain requests, but the patch does not establish that the attacker can repeatedly control the overlap with `tb_stop()`.
4. Primitive and severity interpretation
The exact primitive is a real use-after-free read or stale-pointer use. `tb_xdp_handle_request()` retains a pointer to UUID storage embedded in `tb->root_switch` after dropping `tb->lock`. `tb_stop()` can concurrently remove the root switch and invalidate that storage. The fix changes the UUID reference into an independently allocated copy while still holding the lock, preventing later use of root-switch-owned memory.
This is an active structured-object lifetime violation, but the demonstrated stale access is narrow. It reads an embedded UUID and performs root-switch-dependent lookup behavior during teardown. The evidence does not show attacker-controlled reuse of the freed root-switch allocation, consumption of reclaimed callback or operation fields, an arbitrary or directed write, a refcount takeover, information disclosure, or a security-boundary bypass.
The issue is therefore `CLASS_B`, not `CLASS_A`. The demonstrated consequence is potential kernel crash or denial of service during a shutdown race. Privilege escalation, confidentiality impact, and integrity impact remain speculative and are not scored. The issue is not a strong Important candidate because the patch does not establish meaningful exploitation leverage beyond the constrained stale read. Automatic downgrade is allowed because this is a constrained teardown-time UAF without demonstrated reuse or lifetime-mutating post-free behavior.
Likely operational severity is a limited adjacent-attacker or connected-device denial-of-service issue. It merits review where Thunderbolt XDomain is enabled and untrusted or semi-trusted Thunderbolt peers may be attached.
5. One-sentence report phrase
A connected Thunderbolt XDomain peer can race request handling with domain shutdown, causing use of a stale root-switch UUID pointer and a potential kernel crash, but the patch does not demonstrate controlled reuse, data disclosure, or privilege escalation.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
The patch establishes a real kernel UAF in an adjacent-device request path, but the stale use is limited to root-switch UUID handling during teardown and no concrete post-free exploitation primitive is shown.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: thunderbolt: Set tb->root_switch to NULL when domain is stopped [ Upstream
Commit: f06e9fbae78a51832211b4495a19412c7d49ecb4
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f06e9fbae78a51832211b4495a19412c7d49ecb4
Changed files:
drivers/thunderbolt/tb.c
drivers/thunderbolt/xdomain.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=f06e9fbae78a51832211b4495a19412c7d49ecb4
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97508 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97508
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:H
The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
The Best / paranoid CVSS score: 6.4
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: 3
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).
^ permalink raw reply [relevance 21%]
Results 1-1 of 1 | reverse | sort options + mbox downloads above
-- links below jump to the message on this page --
2026-09-24 21:29 21% [CVE-2026-97508][MODERATE REGULAR] thunderbolt: Set tb->root_switch to NULL when domain is stopped [ Upstream AL-KERNEL
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox