* [CVE-2026-98690][LOW] thunderbolt: Fix domain reference leak when DPRX read is canceled
@ 2026-10-19 4:48 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-19 4:48 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98690
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: thunderbolt: Fix domain reference leak when DPRX read is canceled
Commit: 2f5893172fc6153f5f1ef34014ddbfcbf1f47f29
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2f5893172fc6153f5f1ef34014ddbfcbf1f47f29
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98690
Analysis date: Mon, 19 Oct 2026 00:48:20 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
Canceling Thunderbolt DPRX work can leak a domain reference and make privileged driver unbind wait indefinitely, causing a constrained local denial of service without memory corruption or privilege escalation.
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ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98690 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98690
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-2026-98690 LOW https://www.kernelcve.org/list/?q=CVE-2026-98690 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=0 LEGACY=LOW RESULT=SAME (final reconciliation agrees; DECISION: both LOW) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.1';DESCR 'A Thunderbolt domain reference can be leaked when delayed DPRX work is canceled before tb_dp_tunnel_active runs. The retained reference prevents domain release from completing and can make driver unbind wait indefinitely. Triggering requires a DisplayPort tunnel to be torn down before the DPRX read completes, for example by unplugging the device within the timeout, followed by driver unbind. For the CVSS the PR:H reflects that driver unbind normally requires administrative control on the host. AC:H reflects the required teardown sequence and timing window. The issue is not network reachable. The demonstrated impact is denial of service in the Thunderbolt driver removal path, with no supported memory corruption or privilege escalation primitive. The paranoid availability impact is higher only if the blocked completion also stalls a wider device removal or shutdown operation. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.1 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. The independent weaker Aegis shadow evaluated CVSS 1.7 and ActionableScore 0 with primitive class CLASS_C and manual review NO. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) MAYBE SIMPLEFIX LEAK LINUS - - checked
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ACTIONABLESCORE ANALYSIS
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ActionableScore=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* No floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Concrete persistent kernel reference leak. `tb_domain_get()` acquires a domain reference that is not released when the delayed DPRX work is canceled.
* +1 Availability impact. The retained reference can make `tb_domain_release()` wait indefinitely during driver unbind.
* -2 Proven host-admin-equivalent requirement. The complete demonstrated trigger includes unbinding the Thunderbolt driver, which is a host device-management operation requiring administrative control.
* No UAF or post-lifetime access is established. The defect retains the domain rather than releasing it too early.
* No repeated release or stale refcount mutation exists. The patch adds a missing `tb_domain_put()` to the cancellation path.
* No heap OOB write, active-state corruption, shared-backing write, authorization bypass, disclosure, or integrity primitive is established.
* No remote or namespace-scoped trigger is established.
* No extra DoS point is awarded because the same indefinite unbind wait is the only availability consequence.
* B5-R, B3-PENDING, B4-PENDING, V32, V33, and V34 do not apply.
3. Reachability analysis
The demonstrated sequence requires a DisplayPort tunnel to be torn down before its DPRX read completes, followed by Thunderbolt driver unbind. A physical unplug within the timeout is one trigger for the first stage, but physical access alone cannot perform the privileged unbind stage. The complete chain therefore requires host device-management authority.
No network namespace or delegated capability path is involved. Thunderbolt hardware and an active DisplayPort tunnel are prerequisites, but no additional rarity penalty is applied because the defect is not restricted to an unusually obscure device. The timing condition is deliberate and repeatable enough that no separate hard-race penalty is applied.
4. Primitive and severity interpretation
The exact primitive is a persistent domain-reference leak caused by cancellation of delayed DPRX work before the callback releases the reference. The object remains alive, so this is not a UAF, stale-object access, double release, or memory corruption.
The demonstrated consequence is an indefinite completion wait during driver unbind. A wider shutdown stall is conceivable but is not independently established and receives no paranoid bonus. There is no leverage beyond resource retention and device-removal-path denial of service.
`PrimitiveClass=CLASS_C` reflects a constrained availability failure without an independently useful corruption primitive. `ImportantCandidate=NO` and `AutoDowngradeAllowed=YES` are appropriate because host-admin access is required and no unresolved memory, integrity, authorization, or cross-boundary primitive remains.
5. One-sentence report phrase
Canceling Thunderbolt DPRX work can leak a domain reference and make privileged driver unbind wait indefinitely, causing a constrained local denial of service without memory corruption or privilege escalation.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch establishes a host-admin-triggered reference leak and unbind hang, with no UAF, corruption, authorization bypass, network exposure, or unresolved security-boundary primitive.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: thunderbolt: Fix domain reference leak when DPRX read is canceled
Commit: 2f5893172fc6153f5f1ef34014ddbfcbf1f47f29
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2f5893172fc6153f5f1ef34014ddbfcbf1f47f29
Commit description:
tb_tunnel_one_dp() takes a domain reference which is only dropped once
tb_dp_tunnel_active() has run on the work queue. If that work is
cancelled that reference is leaked. Since
commit f5cc545 ("thunderbolt: Wait for tb_domain_release() to
complete when driver is removed") instead of just leaking memory this
now also blocks in the completion wait forever when unbinding the
driver.
This can be triggered whenever a DP tunnel is torn down before the DPRX
read has completed, e.g. by unplugging within the timeout, and then
unbinding the driver.
That reference only exists to keep the domain around while the DPRX work
is scheduled so let the work itself own it: take it in tb_dp_dprx_start()
and drop it in both places that end the work. Get/put are then paired
inside the same file and it doesn't matter anymore if the callback ever
runs.
Fixes: d6d458d ("thunderbolt: Handle DisplayPort tunnel activation asynchronously")
Cc: [email protected]
Signed-off-by: Sven Peter <[email protected]>
Signed-off-by: Mika Westerberg <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/thunderbolt/tb.c
drivers/thunderbolt/tunnel.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=2f5893172fc6153f5f1ef34014ddbfcbf1f47f29
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98690 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98690
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:H/PR:H/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 4.1
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: 0
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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