From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-63901][MODERATE 7.0] USB: serial: digi_acceleport: fix memory corruption with small endpoints Date: Sun, 19 Jul 2026 21:22:51 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-63901 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: fd34198c2e5d164b57a7dcd4692626fece319225 List-Id: CVE: CVE-2026-63901 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: USB: serial: digi_acceleport: fix memory corruption with small endpoints Commit: fd34198c2e5d164b57a7dcd4692626fece319225 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fd34198c2e5d164b57a7dcd4692626fece319225 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63901 Analysis date: Sun, 19 Jul 2026 21:22:51 -0400 ActionableScore: 6 ActionableScore lower bound: 5 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A malicious USB serial device can advertise too-small bulk-out endpoint buffers and trigger out-of-bounds access or slab corruption in the digi_acceleport driver, making this a physical-access kernel memory corruption issue with DoS impact and plausible but unproven privilege-escalation risk. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63901 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63901 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-2026-63901 MODERATE CHECK WITH IMPACT FROM ORIG NN IMPORTANT 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:H/A:H';*CWE-787;CWE-122;*CWE-20;BEST CVSS score: '6.8';DESCR 'A malicious USB serial device can report bulk-out endpoint buffers that are smaller than the digi_acceleport driver expects. This can make the driver perform out-of-bounds memory accesses or corrupt slab memory during device startup and later port handling. For the CVSS the PR:N because the attacker does not need a user account or kernel privileges on the victim, but must be able to attach or supply a crafted USB device. The issue is physical rather than network reachable. Impact is at least denial of service through kernel memory corruption and may include confidentiality or integrity compromise because the bug class is explicit kernel memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 6) YES WRITE OOB USB PRINTF-TTY HARDWARE LINUS KPANIC KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7 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 Conservative signals: * Memory corruption, Strong corruption primitive: +2 The commit explicitly says the missing endpoint size checks can cause out-of-bounds memory accesses or slab corruption. * Reliable kernel crash / strong DoS: +1 Kernel heap or slab corruption in a USB serial driver is a realistic crash path. * Privileged kernel/device-management memory corruption path: +1 The corruption occurs in a trusted kernel USB serial driver during device startup and port handling, based on device-reported endpoint sizes. * Confidentiality impact plausible: +1 Kernel slab corruption can plausibly affect adjacent kernel objects, although no concrete info leak is demonstrated. * Integrity impact plausible: +1 Slab corruption can plausibly corrupt kernel state, although no controlled overwrite or LPE chain is shown. * Physical-only or rare hardware-only condition: -2 The attacker needs to attach or supply a malicious USB device. This is not network reachable. Conservative total: 5 Paranoid additional signal: * Weak LPE concern: +1 Because the patch explicitly fixes kernel slab corruption reachable from attacker-controlled USB descriptors, privilege escalation cannot be ruled out, but no reclaim, target control, callback control, or reliable overwrite primitive is demonstrated. Paranoid total: 6 ## 3. Reachability analysis The bug is triggerable by a malicious USB serial device that reports bulk-out endpoint buffers smaller than the digi_acceleport driver expects. No local user account or kernel privilege is needed on the victim in the CVSS sense, but the attacker needs physical access or supply-chain control over a USB device. This is not remotely network reachable. The vulnerable path is driver probe/startup for a specific USB serial driver, so exposure is narrower than core USB or generic TTY code. Auto-loading may occur if the crafted device matches the driver IDs, but practical exploitation depends on the system allowing the device to be attached and bound to the driver. Namespaces and containers do not materially reduce the physical-access requirement. A container user generally cannot trigger this without access to USB device injection or passthrough. Call-site confidence: high, because the changed startup path and the exact sanity checks are visible in the patch. ## 4. Severity interpretation This is stronger than an ordinary Moderate because the patch explicitly prevents out-of-bounds access and slab corruption in kernel space. It is not merely a validation cleanup or warning fix. Realistically, the most likely impact is kernel crash or local system compromise risk from a malicious physical USB device. Theoretical privilege escalation is plausible due to slab corruption, but the patch does not show a reliable attacker-controlled overwrite, reclaim primitive, type confusion, or callback hijack. Therefore this is best handled as Actionable Moderate at minimum, with paranoid treatment up to the lower Important-candidate edge, but not as a clear Critical or remote Important issue. ## 5. One-sentence report phrase A malicious USB serial device can advertise too-small bulk-out endpoint buffers and trigger out-of-bounds access or slab corruption in the digi_acceleport driver, making this a physical-access kernel memory corruption issue with DoS impact and plausible but unproven privilege-escalation risk. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: explicit kernel slab corruption from attacker-controlled USB device descriptors is present, and physical-only reachability lowers exposure but does not make the memory corruption safe to auto-close. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: USB: serial: digi_acceleport: fix memory corruption with small endpoints Commit: fd34198c2e5d164b57a7dcd4692626fece319225 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fd34198c2e5d164b57a7dcd4692626fece319225 Commit description: Add the missing bulk-out buffer size sanity checks to avoid out-of-bounds memory accesses or slab corruption should a malicious device report smaller buffers than expected. Fixes: 1da177e ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Reviewed-by: Greg Kroah-Hartman Signed-off-by: Johan Hovold Signed-off-by: Sasha Levin Changed files: drivers/usb/serial/digi_acceleport.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=fd34198c2e5d164b57a7dcd4692626fece319225 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63901 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63901 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: Not available The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 6.8 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).