From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64351][MODERATE REGULAR] net: usb: kalmia: bound RX frame length in kalmia_rx_fixup() Date: Sat, 25 Jul 2026 12:04:42 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64351 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: 391706889a5112feafdc0c68db3ecc7ed325d09c List-Id: CVE: CVE-2026-64351 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: net: usb: kalmia: bound RX frame length in kalmia_rx_fixup() Commit: 391706889a5112feafdc0c68db3ecc7ed325d09c Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=391706889a5112feafdc0c68db3ecc7ed325d09c Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64351 Analysis date: Sat, 25 Jul 2026 12:04:42 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline Moderate, manual review required Manual review required: YES Summary: A malformed USB Kalmia RX frame can underflow an internal packet length calculation and drive an out-of-bounds read in `kalmia_rx_fixup()`, allowing a malicious device or firmware to crash the kernel and possibly expose limited adjacent memory state. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64351 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64351 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-2026-64351 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:L/I:N/A:H';CWE-125;CWE-191;*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 RX frame in the USB Kalmia network driver can make kalmia_rx_fixup compute usb_packet_length from a buffer that contains only one framing header or a short trailing remainder. The subtraction can underflow a u16 length and lets a device supplied ether_packet_length drive an out-of-bounds read in the receive path. For the CVSS the PR:N because the attacker does not need an account on the host when controlling a malicious or compromised USB modem. The issue is not directly reachable over IP network traffic and normally requires a malicious attached USB device or compromised modem firmware. Impact is primarily denial of service via kernel crash. For the paranoid score, limited confidentiality impact is kept because the primitive is an out-of-bounds read, but there is no clear write primitive or supported privilege escalation path.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline Moderate, manual review required (with actual score 3) YES WRITE OOB USB SIMPLEFIX NETWORK SKB HARDWARE LINUS LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS 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 Moderate, manual review required** ## 2. Signal breakdown Triggered signals: * +1 Firmware-mediated external influence: the malformed RX frame is supplied by a USB Kalmia device or compromised modem firmware. * +1 Reliable kernel crash / strong DoS: the device-controlled length underflow can drive OOB access in RX processing and plausibly crash the kernel. * +1 Availability impact realistic: impact can be host-wide if the OOB access faults in kernel context. * +1 Privileged kernel/device-management memory access path: parsing occurs inside a USB network driver RX path using device-supplied framing fields. * +1 Confidentiality impact plausible, paranoid only: the primitive is an out-of-bounds read, but no clear user-visible disclosure channel is shown. Negative signals: * -2 Physical-only or rare hardware-only condition: exploitation normally requires a malicious attached Samsung Kalmia USB modem or compromised device firmware, not a remote network packet. Not awarded: * No remote/network-triggerable +2, because this is not reachable through ordinary IP traffic. * No privilege escalation +1/+2, because the patch supports OOB read and crash risk, not UAF reclaim, OOB write, arbitrary write, type confusion, or callback control. * No strong generic memory corruption +2, because the described primitive is read-only OOB, not an overwrite. Call-site confidence: high. The patch and commit message directly describe `kalmia_rx_fixup()` RX handling and the affected length calculations. ## 3. Reachability analysis The likely attacker is a malicious USB device, malicious modem firmware, or someone with physical/control access to the affected USB modem. No local user account is needed on the host if the attacker controls the device, but physical or firmware-mediated access is required. Namespaces and containers do not materially reduce the privilege requirement because the trigger is in the host USB network receive path. The path is not broadly default-exposed and depends on the Kalmia USB network driver and compatible hardware being present. ## 4. Severity interpretation This behaves more like a low-to-borderline Moderate issue than an Important-class vulnerability. The theoretical memory-safety concern is real because a device-controlled length can cause an out-of-bounds read in kernel RX processing. Realistic exploitation evidence points mainly to denial of service, with only limited paranoid confidentiality concern and no supported LPE path. ## 5. One-sentence report phrase A malformed USB Kalmia RX frame can underflow an internal packet length calculation and drive an out-of-bounds read in `kalmia_rx_fixup()`, allowing a malicious device or firmware to crash the kernel and possibly expose limited adjacent memory state. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a device-controlled kernel out-of-bounds read in RX handling, so it should not be auto-closed despite the physical or firmware-mediated attack model. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net: usb: kalmia: bound RX frame length in kalmia_rx_fixup() Commit: 391706889a5112feafdc0c68db3ecc7ed325d09c Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=391706889a5112feafdc0c68db3ecc7ed325d09c Commit description: kalmia_rx_fixup() computes usb_packet_length = skb->len - (2 * KALMIA_HEADER_LENGTH) as a u16, guarded only by a pre-loop check that skb->len is at least KALMIA_HEADER_LENGTH, which is 6. A device can deliver a short bulk-IN frame with skb->len in the 6 to 11 range, or leave a short trailing remainder on a later loop iteration. Either case underflows usb_packet_length to about 65530. That bypasses the usb_packet_length < ether_packet_length truncation path. The device-supplied ether_packet_length, a le16 up to 65535 read from header_start[2], then drives a memcmp() and the following skb_trim() and skb_pull() past the end of the rx buffer. The rx buffer is hard_mtu * 10, which is 14000 bytes. That is an out of bounds read. Require both the start and end framing headers to be present before subtracting them, on every loop iteration. Fixes: d402612 ("net/usb: Add Samsung Kalmia driver for Samsung GT-B3730") Cc: stable@vger.kernel.org Signed-off-by: Maoyi Xie Reviewed-by: Andrew Lunn Link: https://patch.msgid.link/178211531778.2216480.12637613349790980750@maoyixie.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman Changed files: drivers/net/usb/kalmia.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=391706889a5112feafdc0c68db3ecc7ed325d09c ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64351 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64351 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: 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).