From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98691][MODERATE REGULAR] thunderbolt: Tear down inactive DP tunnels when the domain is stopped Date: Mon, 19 Oct 2026 06:16:06 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98691 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 2 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 34a6e27c954e5bfc29fead17867c7155d54b6481 List-Id: CVE: CVE-2026-98691 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: thunderbolt: Tear down inactive DP tunnels when the domain is stopped Commit: 34a6e27c954e5bfc29fead17867c7155d54b6481 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=34a6e27c954e5bfc29fead17867c7155d54b6481 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98691 Analysis date: Mon, 19 Oct 2026 06:16:06 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: An inactive Thunderbolt DisplayPort tunnel can leave DPRX work running after partial domain teardown, temporarily blocking unbind until timeout, but the supplied evidence does not establish a use-after-free, kernel crash, or integrity primitive. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98691 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98691 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-98691 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98691 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=MODERATE RESULT=DIFF V39_AEGIS_ONE_STEP_UP=LOW->MODERATE TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC) 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:L';CWE-362;*CWE-664;*CWE-772;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '2';DESCR 'An inactive Thunderbolt DisplayPort tunnel can keep dprx_work queued while tb_stop removes routers and stops the control channel. Because the work can requeue itself until the DPRX timeout expires, flush_workqueue may return without waiting for its final execution and the callback can run against a partially torn down domain. The retained domain reference prevents immediate reclamation of the domain object, but it does not establish that every router or tunnel dependency remains valid during the callback. The directly demonstrated impact is a delayed unbind and temporary loss of Thunderbolt management availability until the timeout expires. For the CVSS the PR:N value is used in the paranoid physical access scenario because a person able to manipulate attached Thunderbolt or DisplayPort hardware may not need an authenticated host account. The issue is not network reachable and no supported information disclosure, memory write, or privilege escalation primitive is established. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 2 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage LOW to MODERATE because KP specialist did not establish a qualifying panic and the cross model evidence reconciliation rule was applied. 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. Exact triggered rule markers were KPANIC_UNSUPPORTED_REMOVED and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.0 and ActionableScore 0 with primitive class CLASS_C and manual review RECOMMENDED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) MAYBE SIMPLEFIX DMAorINTERRUPT LINUS KPANIC_UNSUPPORTED_REMOVED V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw conservative score: 2 * Conservative score: 2 * Raw paranoid score: 2 * Paranoid score: 2 * No floor or cap was applied. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 Weak invalid-state candidate. `dprx_work` can execute after routers have been removed and the control channel has been stopped. * +1 Availability impact. The retained domain reference delays driver unbind and Thunderbolt domain removal until the DPRX timeout expires. * No UAF points. The domain reference is explicitly retained, and the supplied code does not establish access to a freed router, tunnel, or domain object. * No reliable kernel-crash point. The demonstrated consequence is a bounded unbind delay rather than an Oops or panic. * No strong or constrained write point. No OOB write, shared-backing write, refcount mutation, or attacker-directed modification is shown. * No active-state trust-boundary point. There is no attacker-influenced structured-state corruption consumed by a privileged downstream component. * No authorization point. The patch does not alter an access-control decision. * No remote, local-unprivileged, physical-trigger, or host-admin penalty or bonus was applied because the complete attacker-controlled trigger is not established. * No race penalty. The required ordering is asynchronous, but the timeout leaves a meaningful window and the evidence does not show a narrow or unreliable race. 3. Reachability analysis The vulnerable state requires an inactive DisplayPort tunnel with pending `dprx_work` while the Thunderbolt domain is stopped. A host administrator can plausibly reach domain shutdown through driver unbind or device-management operations, but the supplied context does not prove that this is the only trigger. A person manipulating attached Thunderbolt or DisplayPort hardware might influence tunnel activation and teardown, but the complete physical trigger is not established. Therefore `HostAdminRequired` remains `UNKNOWN` rather than being inferred as either `YES` or `NO`. No network, user-namespace, or namespace-scoped capability path is shown. Thunderbolt and DisplayPort hardware is required, but no rarity penalty is applied merely because this is a hardware driver. Repeatability depends on recreating a pending DP activation before domain shutdown, and attacker control over that complete sequence is unresolved. 4. Primitive and severity interpretation The exact demonstrated primitive is asynchronous work executing against a logically torn-down domain while a reference keeps the domain object allocated. This is invalid-state consumption with bounded resource retention, not an established post-free dereference. The state is active and structured, but the supplied diff does not show which router or tunnel fields the callback subsequently consumes. It therefore does not establish an active-object UAF, controlled replacement, callback hijack, repeated release, OOB write, or security-boundary crossing. `PrimitiveClass=CLASS_C` because the demonstrated behavior is temporary unbind blocking and post-teardown execution without an independently useful corruption primitive. `ImportantCandidate=NO` because no concrete memory-corruption or integrity mechanism remains unresolved at Important level. `AutoDowngradeAllowed=YES` because the established consequence is bounded, device-management availability loss. B5-R does not apply because no heap OOB write or retry-accumulated write offset exists. B3-PENDING does not apply because no shared-backing write exists. V32, V33, and V34 do not apply because no SKB checksum metadata or downstream packet-header corruption is involved. B4-PENDING does not apply because there is no DENY-to-ALLOW authorization change. 5. One-sentence report phrase An inactive Thunderbolt DisplayPort tunnel can leave DPRX work running after partial domain teardown, temporarily blocking unbind until timeout, but the supplied evidence does not establish a use-after-free, kernel crash, or integrity primitive. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Review the `dprx_work` callback and tunnel deactivation path to confirm that no router, control-channel, or tunnel dependency can be freed before the final callback, although the current evidence supports only a bounded availability issue. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: thunderbolt: Tear down inactive DP tunnels when the domain is stopped Commit: 34a6e27c954e5bfc29fead17867c7155d54b6481 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=34a6e27c954e5bfc29fead17867c7155d54b6481 Commit description: tb_stop() only tears down DMA tunnels so a DP tunnel that is still waiting for dprx_work to complete keeps that work queued while the routers are removed and the control channel is stopped. The work only stops once the DPRX timeout has passed and because it requeues itself until then the flush_workqueue() in tb_domain_remove() won't wait for its final run. The callback then runs against a domain that is already torn down. A reference to that domain is kept so the completion waiting for that domain to disappear in unbind will block until the timeout is eventually reached. Tear down DP tunnels that are not active yet as well which also cancels that work. Tunnels for displays that are already alive are untouched and keep working. Fixes: d6d458d ("thunderbolt: Handle DisplayPort tunnel activation asynchronously") Cc: stable@vger.kernel.org Signed-off-by: Sven Peter Signed-off-by: Mika Westerberg Signed-off-by: Greg Kroah-Hartman Changed files: drivers/thunderbolt/tb.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=34a6e27c954e5bfc29fead17867c7155d54b6481 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98691 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98691 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:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS score: 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: unknown 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: 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 alexanjelausa@gmail.com (and both send reply to CVE record itself too and see "reply" button below for howto reply).