From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-63900][MODERATE REGULAR] USB: serial: keyspan: fix missing indat transfer sanity check Date: Sun, 19 Jul 2026 13:13:32 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-63900 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: bd6c5fe59f374b63173afe5cf0ab38a9a370f2c1 List-Id: CVE: CVE-2026-63900 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: USB: serial: keyspan: fix missing indat transfer sanity check Commit: bd6c5fe59f374b63173afe5cf0ab38a9a370f2c1 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bd6c5fe59f374b63173afe5cf0ab38a9a370f2c1 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63900 Analysis date: Sun, 19 Jul 2026 13:13:32 -0400 ActionableScore: 2 ActionableScore lower bound: 1 Actionable bucket: Ordinary Moderate / Low-like with manual review recommended Manual review required: YES Summary: A malformed Keyspan USB serial indat transfer can cause the kernel driver to parse stale or uninitialized slab data when fewer than 3 bytes remain in the URB buffer, requiring malicious physical USB device access and mainly posing limited information exposure risk. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63900 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63900 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-2026-63900 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:L/A:H';CWE-125;CWE-908;*CWE-20;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '5.7';DESCR 'A malformed usa49wg indat transfer in the USB serial keyspan driver can be parsed when fewer than 3 bytes remain in the URB data buffer. This may cause usa49wg_indat_callback() to read stale or uninitialized slab data and treat it as protocol fields such as port or length. For the CVSS the PR:N is used because a malicious USB device can trigger the parser without a local user account on the host. The attack vector is physical because the attacker needs a malicious or compromised USB serial device attached to the target system. Impact is mainly limited information exposure and denial of service. In the paranoid interpretation, unintended parsing of stale data may also cause limited integrity impact, but the patch does not support an arbitrary write or clear privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like with manual review recommended (with actual score 2) YES USB PRINTF-TTY SIMPLEFIX IMPROVEONLY LINUS PACKET INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK 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 / Low-like with manual review recommended** ## 2. Signal breakdown * **+1 Firmware-mediated external influence:** a malicious or faulty USB serial device can influence the URB payload and transfer length. * **+1 Confidentiality impact plausible:** the commit explicitly says stale or uninitialised slab data may be parsed, which can imply limited kernel memory exposure depending on later serial data handling. * **+1 Weak or indirect corruption candidate, paranoid only:** stale bytes may be interpreted as protocol fields such as port or length, but the patch does not show an OOB write, UAF, type confusion, or attacker-controlled overwrite. * **-2 Physical-only or rare hardware-only condition:** practical triggering requires attaching or controlling a specific USB serial device path. * **No strong DoS point:** no reliable kernel crash, BUG, panic, or persistent host-wide failure is described. * **No LPE point:** there is no demonstrated reclaim, overwrite, callback control, refcount abuse, or arbitrary write primitive. Call-site confidence: **medium**. The affected callback and commit message are visible, but the full downstream TTY data flow is not included. ## 3. Reachability analysis The bug is triggerable by a malicious, compromised, or malformed Keyspan-compatible USB serial device sending a short `usa49wg` indat transfer. No local user account is required on the host, but the attacker needs physical or device-level access, so this is not network reachable. Namespaces and containers do not materially reduce the requirement because the vulnerable input comes from USB hardware into the host kernel driver. The path is only relevant when the Keyspan USB serial driver is available and a matching device is attached, although module autoloading may make the driver reachable after device insertion. ## 4. Severity interpretation This behaves more like a **Low-like or ordinary Moderate** issue than an Important-class kernel vulnerability. The realistic impact is limited stale or uninitialized slab data parsing from a physical USB device, with possible limited information exposure. The theoretical concern is that stale bytes can influence protocol parsing, but there is no evidence of a write primitive, UAF, controlled object replacement, privilege escalation, or reliable kernel crash. ## 5. One-sentence report phrase A malformed Keyspan USB serial indat transfer can cause the kernel driver to parse stale or uninitialized slab data when fewer than 3 bytes remain in the URB buffer, requiring malicious physical USB device access and mainly posing limited information exposure risk. ## 6. Manual review recommendation **MANUAL CHECK RECOMMENDED** Manual review is recommended because this is an OOB or uninitialized-data parsing issue in a kernel USB driver, but it should not be treated as an Important candidate without additional evidence of disclosure, crash reliability, or memory corruption beyond stale data parsing. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: USB: serial: keyspan: fix missing indat transfer sanity check Commit: bd6c5fe59f374b63173afe5cf0ab38a9a370f2c1 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bd6c5fe59f374b63173afe5cf0ab38a9a370f2c1 Commit description: Add the missing sanity check on the size of usa49wg indat transfers to avoid parsing stale or uninitialised slab data. Fixes: 0ca1268 ("USB Serial Keyspan: add support for USA-49WG & USA-28XG") Cc: stable@vger.kernel.org # 2.6.23 Reviewed-by: Greg Kroah-Hartman Signed-off-by: Johan Hovold Signed-off-by: Greg Kroah-Hartman Changed files: drivers/usb/serial/keyspan.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=bd6c5fe59f374b63173afe5cf0ab38a9a370f2c1 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63900 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63900 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:L/I:L/A:H The Best / paranoid CVSS score: 5.7 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).