From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74455][MODERATE REGULAR] can: peak_usb: validate uCAN receive record lengths Date: Sat, 15 Aug 2026 19:12:27 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74455 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: 3 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: 6067c878e38d02a3d5c43497347e143f85c9064a List-Id: CVE: CVE-2026-74455 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: can: peak_usb: validate uCAN receive record lengths Commit: 6067c878e38d02a3d5c43497347e143f85c9064a Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6067c878e38d02a3d5c43497347e143f85c9064a Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74455 Analysis date: Sat, 15 Aug 2026 19:12:27 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: Malformed uCAN records from a PEAK USB CANFD adapter can trigger OOB reads in the peak_usb receive parser and may disclose limited kernel memory through skb data or cause a device-triggered DoS. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74455 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74455 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-2026-74455 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:H/I:N/A:L';CWE-125;CWE-126;*CWE-20;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '5.2';DESCR 'A malformed uCAN receive record from a PEAK USB CANFD adapter can be shorter than the fixed header required for its record type or shorter than the CAN payload length later copied into an skb. This can make pcan_usb_fd_decode_buf or pcan_usb_fd_decode_canmsg read beyond the valid record data and may copy unintended kernel memory bytes into the received CAN frame. For the CVSS the PR:N is used because a malicious or compromised USB device does not need an authenticated local account on the victim. The issue is not directly network reachable through IP traffic and normally requires physical access to the USB device path or control of the adapter firmware. Impact is at least limited confidentiality exposure and possible denial of service, with no clear write primitive or direct privilege escalation shown by the patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) YES USB ERRORPATH NETWORK SKB LINUS PACKET DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Borderline / manual review recommended** ## 2. Signal breakdown Conservative signals: * Firmware-mediated external influence: +1 Malformed uCAN records are supplied through a USB CANFD adapter. A malicious or compromised adapter firmware could control this input. * Confidentiality impact plausible: +1 The missing record-length checks can cause OOB reads from the USB receive buffer area, and CAN payload bytes may be copied into an skb. * Physical-only or rare hardware-only condition: -1 This requires the PEAK USB CANFD device path or control of device firmware, not normal remote network access. Paranoid additional signal: * Availability impact realistic: +1 Depending on allocation layout and debug settings, malformed short records could plausibly cause a driver fault or kernel warning/crash, although the patch mainly supports OOB read rather than a reliable crash primitive. Not awarded: * No remote/network-triggerable signal. This is USB device input, not IP or CAN network traffic directly. * No privilege escalation signal. The patch does not show UAF, OOB write, reclaim, callback control, refcount abuse, or type confusion. * No strong generic memory corruption signal. The supported primitive is read-side bounds failure, not attacker-controlled overwrite. ## 3. Reachability analysis The most realistic attacker is someone who can attach or control a PEAK USB CANFD adapter, or compromise its firmware so that it emits malformed uCAN receive records. A normal remote network attacker cannot directly shape the USB record layout unless there is an additional firmware or device-level compromise. Local namespaces and containers do not materially lower privileges because the vulnerable input comes from the physical USB device path rather than a namespaced local syscall API. The path is only present when the peak_usb driver and affected CANFD USB hardware are used. Call-site confidence: high. The patch includes the relevant parsing path, pcan_usb_fd_decode_buf(), and the CAN frame decode path, pcan_usb_fd_decode_canmsg(). ## 4. Severity interpretation This behaves more like a low-to-borderline Moderate issue than an Important-class vulnerability. Theoretical impact includes limited kernel memory disclosure through OOB reads into received CAN frames and possible local/device-triggered DoS. Realistic exploitation is constrained by the need for physical/device/firmware control and there is no demonstrated write primitive or privilege escalation path. ## 5. One-sentence report phrase Malformed uCAN records from a PEAK USB CANFD adapter can trigger OOB reads in the peak_usb receive parser and may disclose limited kernel memory through skb data or cause a device-triggered DoS. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Manual review is recommended because this is an OOB read and possible information leak candidate, but it is not directly network reachable and the patch does not support a strong memory corruption or LPE primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: can: peak_usb: validate uCAN receive record lengths Commit: 6067c878e38d02a3d5c43497347e143f85c9064a Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6067c878e38d02a3d5c43497347e143f85c9064a Commit description: pcan_usb_fd_decode_buf() walks uCAN records packed in one USB receive buffer. Require each record to contain the fixed header for its type, and verify CAN payload bytes before copying them into the skb. Signed-off-by: Pengpeng Hou Link: https://patch.msgid.link/20260706092836.79754-1-pengpeng@iscas.ac.cn Fixes: 0a25e1f ("can: peak_usb: add support for PEAK new CANFD USB adapters") Cc: stable@vger.kernel.org Signed-off-by: Marc Kleine-Budde Signed-off-by: Greg Kroah-Hartman Changed files: drivers/net/can/usb/peak_usb/pcan_usb_fd.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=6067c878e38d02a3d5c43497347e143f85c9064a ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74455 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74455 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:L/I:N/A:L The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:L 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: 2 Paranoid ActionableScore: 3 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).