From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74460][MODERATE REGULAR] can: ems_usb: validate CPC message lengths Date: Sat, 15 Aug 2026 15:25:56 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74460 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: 1 X-AL-KERNEL-ActionableScore-Lower: 0 X-AL-KERNEL-Commit: ce8125566b1d0b0f16449407e014addf451804ea List-Id: CVE: CVE-2026-74460 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: can: ems_usb: validate CPC message lengths Commit: ce8125566b1d0b0f16449407e014addf451804ea Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ce8125566b1d0b0f16449407e014addf451804ea Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74460 Analysis date: Sat, 15 Aug 2026 15:25:56 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like with manual review due to kernel OOB read Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74460 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74460 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: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-74460 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H';CWE-125;CWE-130;*CWE-20;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.2';DESCR 'A malformed CPC message from an EMS CPC USB CAN adapter can be parsed without first proving that the declared message length fits inside the URB payload. The same receive path can also call CAN frame, CAN state, CAN error, or overrun handlers when the type-specific payload is shorter than the fields those handlers read. This creates an out-of-bounds read condition in the kernel USB receive callback. The issue is not network reachable over IP and normally requires a malicious or compromised USB CAN device, direct physical access to attach such a device, or an equivalent setup where the USB device side is attacker controlled. For the CVSS the PR:N is used because the attacker does not need an authenticated local account on the host once crafted CPC messages can be supplied by the USB device. Impact is at least denial of service via invalid kernel reads and possible kernel crash. A limited confidentiality impact is also defensible if stale bytes from the receive buffer are propagated into CAN frames visible to local consumers.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like with manual review due to kernel OOB read (with actual score 1) YES DANGER USB ERRORPATH NETWORK LINUS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ActionableScoreLower=0 ### 1. ActionableScore * Conservative score: 0 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate / Low-like with manual review due to kernel OOB read** ### 2. Signal breakdown Conservative signals: * Firmware-mediated or device-mediated external influence: +1 The malformed input is supplied by the USB CAN device side, not by ordinary local userspace or the IP network. * Reliable kernel crash / strong DoS: +1 Missing length validation can make receive handlers read fields beyond the valid CPC message payload. This can plausibly crash the kernel depending on buffer layout. * Physical-only or rare hardware-only condition: -2 Practical triggering normally requires a malicious or compromised EMS CPC USB CAN adapter, physical access, or control over the USB device endpoint. Conservative total: 0 Paranoid additional signal: * Confidentiality impact plausible: +1 A limited OOB read could potentially consume stale bytes from the receive buffer and propagate them into CAN-visible data paths, but no strong information disclosure primitive is demonstrated. Paranoid total: 1 Not awarded: * No remote/network-triggerable +2 because this is not reachable over IP or ordinary CAN network traffic without a malicious USB device endpoint. * No generic strong memory corruption +2 because the patch shows bounds validation for reads, not OOB write, UAF, double free, type confusion, or controlled overwrite. * No privilege escalation plausible +2 because there is no reclaim, write primitive, callback control, refcount abuse, or object replacement shown. ### 3. Reachability analysis The likely attacker must control the USB device side of an EMS CPC USB CAN adapter or attach a malicious USB device that presents malformed CPC messages. A normal local unprivileged user cannot trigger this solely through syscalls unless they can influence the USB device firmware or physical device behavior. Containers and namespaces do not materially reduce the requirement, because the vulnerable input arrives from the USB hardware path. The driver is not a broad default remote attack surface and depends on specific CAN USB hardware being connected and active. ### 4. Severity interpretation This behaves more like an ordinary Moderate / Low-like issue in practical deployment because exploitation is physical or device-mediated and the demonstrated primitive is a bounded receive-path validation failure leading mainly to OOB reads and possible crash. The theoretical memory-safety concern is real enough for manual review, but the patch does not support arbitrary write, UAF, privilege escalation, or remote network reachability. ### 5. One-sentence report phrase Malformed CPC messages from an EMS CPC USB CAN device can bypass message length validation in ems_usb_read_bulk_callback and cause kernel out-of-bounds reads, with realistic impact limited mainly to physical or device-mediated DoS and possible limited information exposure. ### 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the score is low due to physical/device-mediated reachability, but the bug is still a kernel receive-path OOB read with a plausible crash and limited confidentiality concern, so it should not be blindly auto-closed without confirming actual data propagation and crash behavior. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: can: ems_usb: validate CPC message lengths Commit: ce8125566b1d0b0f16449407e014addf451804ea Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ce8125566b1d0b0f16449407e014addf451804ea Commit description: ems_usb_read_bulk_callback() walks CPC messages packed in one USB receive buffer. Check that each declared message fits in the URB payload. Also require the type-specific payload to cover the fields used by the CAN, state, error and overrun handlers. Signed-off-by: Pengpeng Hou Link: https://patch.msgid.link/20260706092752.79600-1-pengpeng@iscas.ac.cn Fixes: 702171a ("ems_usb: Added support for EMS CPC-USB/ARM7 CAN/USB interface") Cc: stable@vger.kernel.org Signed-off-by: Marc Kleine-Budde Signed-off-by: Greg Kroah-Hartman Changed files: drivers/net/can/usb/ems_usb.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=ce8125566b1d0b0f16449407e014addf451804ea ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74460 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74460 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:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H The Best / paranoid CVSS score: 5.2 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: 0 Paranoid ActionableScore: 1 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).