From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98761][LOW] usb: typec: tcpm: recover after failure to start the frs ams Date: Sat, 24 Oct 2026 04:51:07 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98761 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 0 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 184d842121e7d1fbc3a81895f36f72fa27444163 List-Id: CVE: CVE-2026-98761 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: usb: typec: tcpm: recover after failure to start the frs ams Commit: 184d842121e7d1fbc3a81895f36f72fa27444163 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=184d842121e7d1fbc3a81895f36f72fa27444163 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98761 Analysis date: Sat, 24 Oct 2026 04:51:07 -0400 ActionableScore: 0 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: A physically triggered failed FRS transition can leave USB-C VBUS enabled after disconnect because the TCPM state machine omits error recovery. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98761 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98761 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-2026-98761 LOW https://www.kernelcve.org/list/?q=CVE-2026-98761 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE AEGIS_AS=1 LEGACY=LOW RESULT=DIFF (final Legacy and Aegis differ; FINAL: LOW, Aegis: MODERATE) 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-754;CWE-404;CWE-459;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.2';DESCR 'A logic and incomplete recovery flaw occurs when FAST_ROLE_SWAP AMS cannot start after an anomalous FRS signal during cable disconnection. The TCPC may already have started sourcing VBUS, while the EAGAIN path only selects INVALID_STATE and does not reset the port, allowing VBUS to remain enabled after disconnect. This can affect USB Type C port availability and may create power contention, but no invalid memory access, information leak, or memory write primitive is shown. For the CVSS the PR:N value is used because no authenticated software privilege is required, although reliable triggering requires physical access and a cable or partner capable of producing an anomalous FRS signal during disconnect. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 4.2 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage IMPORTANT to MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE_KPANIC to LOW because the ActionableScore threshold rule was applied. final reconciliation stage LOW to LOW 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 LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 and KPANIC_UNSUPPORTED_REMOVED and V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED. The independent weaker Aegis shadow evaluated CVSS 2.0 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The models disagreed but the aggregation rules retained the production result. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) MAYBE REMOTE DANGER USB NETWORK LINUS LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=0 PrimitiveClass=NONE RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: -1 (+1 device-port availability impact, -2 physical trigger requirement). * Conservative score: 0, applying the score-range lower bound. * Raw paranoid score: -1; no technically supported additional effect. * Paranoid score: 0, applying the score-range lower bound. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1: Device-local availability impact. Failure recovery leaves VBUS sourcing enabled after cable disconnection and may leave the Type-C port in an invalid operational state. * -2: Physical-only trigger. The evidenced trigger is an anomalous FRS signal from a cable or attached partner during physical disconnection. * No memory corruption, UAF, OOB access, persistent kernel-resource leak, authorization bypass, host-wide crash, or protected-state corruption is shown. * B5-R does not apply: there is no heap OOB write, retry-accumulated index, or later consumption of corrupted structured memory. * B3-PENDING does not apply: no shared/file-backed storage write exists. * B4-PENDING does not apply: the patch changes state-machine recovery, not a DENY-to-ALLOW authorization decision. 3. Reachability analysis A physically connected cable or partner that incorrectly emits an FRS signal during disconnect can trigger the condition without host software privileges or UID 0. No namespace capability, prior privileged software setup, ioctl path, or remotely reachable packet path is involved. Timing depends on the anomalous signal coinciding with disconnection, but no separate race penalty is applied because physical access already captures the principal restriction. 4. Primitive and severity reading The exact defect is incomplete Type-C state-machine recovery: `-EAGAIN` from `tcpm_ams_start()` previously selected `INVALID_STATE` rather than initiating `ERROR_RECOVERY`, allowing autonomously enabled VBUS sourcing to remain on. This is device/power-state mismanagement, not kernel memory or authorization corruption. The shown consequence is port disruption and possible power contention; host panic, hardware damage, persistent system-wide denial of service, and attacker-controlled writes are unproven. Therefore the primitive class is NONE, no Important review candidate exists, and automatic downgrade is allowed. 5. One-sentence report phrase A physically triggered failed FRS transition can leave USB-C VBUS enabled after disconnect because the TCPM state machine omits error recovery. 6. Manual review advice NO MANUAL CHECK NEEDED The patch supports only a physically triggered, device-local recovery and availability defect without a security primitive. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: usb: typec: tcpm: recover after failure to start the frs ams Commit: 184d842121e7d1fbc3a81895f36f72fa27444163 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=184d842121e7d1fbc3a81895f36f72fa27444163 Commit description: Reset the port if the tcpm fails to start the FAST_ROLE_SWAP AMS by initiating error recovery on it. This helps in cases where some cables (incorrectly) signal an FRS to an FRS capable port during disconnection. The TCPC autonomously starts sourcing VBUS on detecting the FRS signal. However, the VBUS sourcing is left on when the FAST_ROLE_SWAP AMS fails to start (as tcpm_sink_tx_ok is 0 as CC is open due to the cable disconnect). This is because the code sets the state to INVALID_STATE without resetting the port state. Log snippet before changes: [ 101.401960] AMS FAST_ROLE_SWAP start [ 101.401971] Sink TX No Go [ 101.401982] sourcing vbus [ 101.401987] VBUS on [ 101.402159] VBUS on [ 109.257809] CC1: 0 -> 0, CC2: 5 -> 0 [state SNK_READY, polarity 1, disconnected] [ 111.267442] VBUS on After changes: [ 70.541211] AMS FAST_ROLE_SWAP start [ 70.541220] Sink TX No Go [ 70.541228] state change SNK_READY -> ERROR_RECOVERY [rev3 NONE_AMS] [ 70.541362] VBUS on [ 70.541365] sourcing vbus [ 70.541367] VBUS on [ 70.541374] state change ERROR_RECOVERY -> PORT_RESET [rev3 NONE_AMS] [ 70.541410] disable vbus discharge ret:0 [ 70.543028] Setting usb_comm capable false [ 70.544009] Setting voltage/current limit 0 mV 0 mA [ 70.544034] polarity 0 [ 70.544239] Requesting mux state 0, usb-role 0, orientation 0 [ 70.555550] cc:=0 [ 70.555595] pending state change PORT_RESET -> PORT_RESET_WAIT_OFF @ 100 ms [rev3 NONE_AMS] [ 70.555697] VBUS off [ 70.555702] VBUS VSAFE0V [ 70.555762] CC1: 5 -> 0, CC2: 0 -> 0 [state PORT_RESET, polarity 0, disconnected] [ 70.587794] VBUS off [ 70.587799] VBUS VSAFE0V [ 70.655672] state change PORT_RESET -> PORT_RESET_WAIT_OFF [delayed 100 ms] [ 70.655682] state change PORT_RESET_WAIT_OFF -> SNK_UNATTACHED [rev3 NONE_AMS] [ 70.655686] Start toggling [ 70.656274] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected] Fixes: 0908c5a ("usb: typec: tcpm: AMS and Collision Avoidance") Cc: stable Signed-off-by: Amit Sunil Dhamne Reviewed-by: Badhri Jagan Sridharan Acked-by: Heikki Krogerus Link: https://patch.msgid.link/20260903-frs-error-handling-v1-1-ad0fee541847@google.com Signed-off-by: Greg Kroah-Hartman Changed files: drivers/usb/typec/tcpm/tcpm.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=184d842121e7d1fbc3a81895f36f72fa27444163 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98761 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98761 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: 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 alexanjelausa@gmail.com (and both send reply to CVE record itself too and see "reply" button below for howto reply).