From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-63958][MODERATE 7.0] usb: typec: ucsi: validate connector number in ucsi_connector_change() Date: Sun, 19 Jul 2026 18:36:50 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-63958 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 6 X-AL-KERNEL-ActionableScore-Lower: 5 X-AL-KERNEL-Commit: cea949203faef9cb783adc7b978cce056271e057 List-Id: CVE: CVE-2026-63958 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: usb: typec: ucsi: validate connector number in ucsi_connector_change() Commit: cea949203faef9cb783adc7b978cce056271e057 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cea949203faef9cb783adc7b978cce056271e057 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63958 Analysis date: Sun, 19 Jul 2026 18:36:50 -0400 ActionableScore: 6 ActionableScore lower bound: 5 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A malicious or buggy UCSI PPM can supply an invalid connector number that makes `ucsi_connector_change()` schedule work on memory past the connector array, causing a likely kernel crash and a constrained memory-corruption risk. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63958 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63958 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. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-63958 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';CWE-129;*CWE-787;*CWE-20;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '6.4';DESCR 'A UCSI connector change notification can carry an invalid 7-bit connector number supplied by the PPM. ucsi_connector_change used that value to index the connector array before checking it against cap.num_connectors, so a buggy or malicious PPM could make the kernel operate on memory past the end of the array. The dangerous operation is schedule_work on an out-of-bounds work item, which can lead to kernel memory corruption or a crash. For the CVSS the PR:N is used because a malicious or compromised PPM can supply the invalid connector number without a local user account on the host. The issue is not network reachable and is mainly relevant to systems where EC firmware or an attached UCSI controller can emit malformed CCI notifications. Impact is at least local or physical denial of service and in the paranoid case may include confidentiality and integrity impact due to memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 6) YES USB SIMPLEFIX KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=6 ActionableScoreLower=5 ## 1. ActionableScore * Conservative score: 5 * Paranoid score: 6 * Final recommended bucket: **Actionable Moderate at minimum** ## 2. Signal breakdown * Firmware-mediated external influence: +1. The connector number is supplied by the PPM, including EC firmware or an attached UCSI controller. * Memory corruption, weak/indirect corruption candidate: +1. The unchecked connector number is used as an array index and can produce an out-of-bounds `struct ucsi_connector` pointer. * Weak LPE concern: +1. `schedule_work()` is called on an out-of-bounds `work_struct`, which is a corruption sink, but no controlled reclaim, controlled payload, or reliable object replacement is shown. * Reliable kernel crash / strong DoS: +1. Scheduling work on memory past the connector array is likely to cause a crash or workqueue corruption. * Privileged kernel/device-management memory corruption path: +1. The bug is in a trusted USB Type-C UCSI device-management path fed by firmware/controller notifications. * Broad/default/common subsystem exposure: +1. UCSI is common on modern USB Type-C systems, although the malicious input source is platform-specific. * Corruption primitive highly constrained: -1. The attacker influence is mainly the connector number. The target is adjacent kernel memory selected indirectly, not an arbitrary attacker-chosen address or payload. Paranoid-only adjustment: * Confidentiality/integrity impact plausible: +1 effective uplift. Because an out-of-bounds `work_struct` may corrupt kernel workqueue state, limited C/I risk is defensible for manual-review triage, but the score is kept below Important because no concrete exploit primitive is demonstrated. ## 3. Reachability analysis The bug is not network reachable and is not normally triggerable by an unprivileged local user. The realistic trigger is a buggy or malicious PPM, EC firmware, or an attached UCSI controller on transports such as ccg, stm32g0, or glink. Namespaces and containers do not meaningfully lower the privilege requirement because the malformed connector-change notification comes from firmware or device-side control, not from a normal container-visible API. The path may be active by default on systems using UCSI for USB Type-C management, but exploitation requires control over or compromise of the firmware/controller notification source. Call-site confidence: high. The patch shows the unchecked index and the immediate use of `schedule_work(&con->work)` on the derived object. ## 4. Severity interpretation This is stronger than an ordinary Moderate because the patch prevents an out-of-bounds object selection followed by workqueue scheduling on memory past the array. It is not a clean Important by default because the primitive is firmware-mediated, constrained, and lacks evidence of attacker-controlled payload, reclaim, arbitrary write, or demonstrated LPE. Conservative handling is Actionable Moderate. Paranoid handling remains Actionable Moderate at minimum and should not be auto-closed because the bug is a kernel memory-corruption candidate in a privileged device-management path. ## 5. One-sentence report phrase A malicious or buggy UCSI PPM can supply an invalid connector number that makes `ucsi_connector_change()` schedule work on memory past the connector array, causing a likely kernel crash and a constrained memory-corruption risk. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the patch directly fixes an unchecked firmware-supplied array index followed by `schedule_work()` on an out-of-bounds object, making this a constrained but real kernel memory-corruption candidate rather than a pure validation-only or DoS-only issue. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: usb: typec: ucsi: validate connector number in ucsi_connector_change() Commit: cea949203faef9cb783adc7b978cce056271e057 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cea949203faef9cb783adc7b978cce056271e057 Commit description: The connector number in a UCSI CCI notification is a 7-bit field supplied by the PPM. ucsi_connector_change() uses it to index the ucsi->connector[] array without checking it against the number of connectors the PPM reported at init time, so a buggy or malicious PPM (EC firmware, or an I2C-attached UCSI controller on the ccg / stm32g0 / glink transports) can drive schedule_work() on memory past the end of the array. Reject connector numbers that are zero or exceed cap.num_connectors before dereferencing the array. Assisted-by: gkh_clanker_t1000 Cc: Heikki Krogerus Cc: Benson Leung Cc: Jameson Thies Cc: Nathan Rebello Cc: Johan Hovold Cc: Pooja Katiyar Cc: Hsin-Te Yuan Cc: Abel Vesa Cc: stable Reviewed-by: Abel Vesa Reviewed-by: Heikki Krogerus Reviewed-by: Benson Leung Link: https://patch.msgid.link/2026051351-truck-steadfast-df48@gregkh Signed-off-by: Greg Kroah-Hartman Changed files: drivers/usb/typec/ucsi/ucsi.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=cea949203faef9cb783adc7b978cce056271e057 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63958 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63958 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:L/I:L/A:H The Best / paranoid CVSS vector: AV:P/AC:H/PR:N/UI:N/S:U/C:H/I:H/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: 5 Paranoid ActionableScore: 6 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).