From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-63961][MODERATE REGULAR] usb: typec: altmodes/displayport: validate count before reading Status Update VDO Date: Sun, 19 Jul 2026 13:26:08 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-63961 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: 1 X-AL-KERNEL-Commit: 74aabe9ea30fdfba924fce9594e6aa69a596a4bb List-Id: CVE: CVE-2026-63961 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: usb: typec: altmodes/displayport: validate count before reading Status Update VDO Commit: 74aabe9ea30fdfba924fce9594e6aa69a596a4bb Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=74aabe9ea30fdfba924fce9594e6aa69a596a4bb Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63961 Analysis date: Sun, 19 Jul 2026 13:26:08 -0400 ActionableScore: 2 ActionableScore lower bound: 1 Actionable bucket: Ordinary Moderate / manual review due to kernel stack information disclosure Manual review required: NO Summary: A malicious USB Type-C DisplayPort Alt Mode device can send a malformed Status Update VDO count, causing the kernel to read uninitialized stack data and potentially disclose it outside the local stack context. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63961 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63961 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-2026-63961 MODERATE CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N';*CWE-457;*CWE-200;*CWE-20;Other CVSS 'AV:P/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N';BEST CVSS score: '4.6';DESCR 'A malicious or malformed USB Type-C DisplayPort Alt Mode device can send a Status Update VDO with an invalid object count, causing the kernel to read uninitialized stack data and send it outside the local stack context. This is an information disclosure issue rather than a memory corruption or crash issue. For the CVSS the PR:N value is used for the paranoid score because no local account or kernel privilege is required once the attacker can present the malicious Type-C device to the target. The issue is not network reachable and requires physical or local device access, typically through a malicious dock, adapter, cable, or directly attached USB-C partner. Impact is confidentiality loss, with no direct integrity or availability impact supported by the patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / manual review due to kernel stack information disclosure (with actual score 2) YES DANGER USB SIMPLEFIX HARDWARE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=1 ## 1. ActionableScore * Conservative score: 1 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / manual review due to kernel stack information disclosure**:: ## 2. Signal breakdown Triggered signals: * Firmware-mediated external influence: +1 A broken or malicious USB Type-C / DisplayPort Alt Mode partner device can provide the malformed Status Update VDO count. * Confidentiality impact plausible: +1 The commit explicitly says the kernel may read uninitialized stack data and send it elsewhere. * Broad/default/common subsystem exposure: +1 USB Type-C and DisplayPort Alt Mode are common on modern laptops and docks, although the vulnerable path requires compatible hardware and altmode negotiation. Subtracted signals: * Physical-only or rare hardware-only condition: -2 The attacker generally needs physical or device-level access through a malicious USB-C device, dock, adapter, cable, or compromised Type-C partner. Not applied: * No generic memory corruption bonus. The patch shows an uninitialized stack read, not UAF, OOB write, double-free, type confusion, or arbitrary write. * No privilege escalation bonus. There is no demonstrated write primitive, control-flow primitive, reclaim primitive, or object lifetime corruption. * No reliable kernel crash / strong DoS bonus. The described impact is information disclosure, not panic or persistent availability loss. Call-site confidence: high. The vulnerable read and the added count check are visible directly in `dp_altmode_vdm()`. ## 3. Reachability analysis The bug is triggerable by a malformed USB Type-C DisplayPort Alt Mode device sending a Status Update VDO with an invalid object count. No local Linux account is required once the attacker can present the malicious device to the target, so the practical privilege requirement is physical/device presence rather than OS privileges. Namespaces and containers do not materially affect reachability because the input arrives through USB Type-C alternate mode handling in the host kernel. The path is not network reachable. It depends on USB Type-C / DisplayPort Alt Mode support, compatible hardware, and a connected or emulated malicious partner device. ## 4. Severity interpretation This behaves like an ordinary Moderate information disclosure issue, not an Important-class memory corruption vulnerability. The theoretical concern is that uninitialized kernel stack data may expose sensitive kernel values or addresses, but the patch does not show attacker-controlled memory corruption, privilege escalation, or a crash primitive. The main reason not to auto-close without review is that kernel stack disclosure can sometimes assist exploitation of other bugs. However, the physical-only attack surface and lack of write or lifetime corruption keep the actionable score low. ## 5. One-sentence report phrase A malicious USB Type-C DisplayPort Alt Mode device can send a malformed Status Update VDO count, causing the kernel to read uninitialized stack data and potentially disclose it outside the local stack context. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Manual review is recommended because this is a kernel stack information disclosure. It is not a strong Important candidate by itself because exploitation requires physical or device-level access and the patch does not indicate memory corruption, privilege escalation, or reliable DoS. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: usb: typec: altmodes/displayport: validate count before reading Status Update VDO Commit: 74aabe9ea30fdfba924fce9594e6aa69a596a4bb Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=74aabe9ea30fdfba924fce9594e6aa69a596a4bb Commit description: A broken/malicious device can send the incorrect count for a status update VDO, which will cause the kernel to read uninitialized stack data and send it off elsewhere. Fix this up by correctly verifying the count for the update object. Assisted-by: gkh_clanker_t1000 Cc: stable Reviewed-by: Heikki Krogerus Link: https://patch.msgid.link/2026051350-reacquire-sculpture-4244@gregkh Signed-off-by: Greg Kroah-Hartman Changed files: drivers/usb/typec/altmodes/displayport.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=74aabe9ea30fdfba924fce9594e6aa69a596a4bb ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63961 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63961 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:L/PR:N/UI:R/S:U/C:L/I:N/A:N The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N The Best / paranoid CVSS score: 4.6 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: 1 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).