From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-68368][MODERATE 7.0] usb: gadget: f_ncm: validate datagram bounds in ncm_unwrap_ntb() Date: Mon, 10 Aug 2026 09:48:07 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-68368 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: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: e07751d0527ccc2a1c32eb0b0b7da3b4b9b5381f List-Id: CVE: CVE-2026-68368 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: usb: gadget: f_ncm: validate datagram bounds in ncm_unwrap_ntb() Commit: e07751d0527ccc2a1c32eb0b0b7da3b4b9b5381f Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e07751d0527ccc2a1c32eb0b0b7da3b4b9b5381f Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68368 Analysis date: Mon, 10 Aug 2026 09:48:07 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: A malicious USB host can craft NCM NTB headers with invalid block or datagram bounds so that `ncm_unwrap_ntb()` copies adjacent kernel memory into a network skb, causing kernel memory disclosure and possible DoS on USB gadget devices exposing f_ncm. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68368 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68368 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-2026-68368 MODERATE CHECK WITH IMPACT FROM ORIG NN IMPORTANT Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H';CWE-125;CWE-126;*CWE-200;*CWE-20;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:L';BEST CVSS score: '8.1';DESCR 'A kernel out-of-bounds read in the USB NCM gadget receive path occurs because ncm_unwrap_ntb() did not fully validate that host supplied NTB block lengths and datagram ranges stay within the available buffer. A malicious USB host can craft NTB headers with offsets or lengths beyond the declared block, or provide a secondary NTB length larger than the remaining skb data, causing skb_put_data() to copy adjacent kernel memory such as skb_shared_info into a network skb. For the CVSS the PR:N is used because the attacker does not need a local account or privileges on the victim device, only the ability to send malformed NCM traffic from the USB host side. The base vector uses AV:P because a USB host relationship normally requires physical or platform level attachment. The paranoid vector uses AV:A when the already connected USB NCM link is treated as an adjacent communication channel. Impact is primarily confidentiality loss through kernel memory disclosure, with possible denial of service if the out-of-bounds read reaches unsafe memory. Integrity impact is not assigned because the patch shows an out-of-bounds read and copy, not an overwrite primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5) YES OOB USB SIMPLEFIX IMPROVEONLY LINUS KPANIC KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7 YES NO guess ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Network-like external data-plane trigger over USB NCM: +2 A malicious USB host can supply crafted NTB packets to the gadget receive path. This is not Internet-remote, but it is externally supplied protocol input once the USB NCM link exists. * Confidentiality impact plausible: +1 The commit explicitly states that `skb_put_data()` can copy adjacent kernel memory, including data near `skb_shared_info`, into a network skb. * Availability impact realistic: +1 The out-of-bounds read may also lead to a crash if the invalid range crosses unsafe memory, although disclosure is the clearer primitive. * Rare or configuration-dependent exposure: -1 The affected path requires USB gadget mode with the NCM function enabled, which is not a default exposure on ordinary servers. * Physical or attached-host style condition: -1 Triggering normally requires control of the USB host side or an equivalent attached host relationship. Paranoid adjustment: * Treat established USB NCM as adjacent protocol reachability and avoid the full physical-only downgrade: +1 net effect In embedded, phone, appliance, or test-lab deployments, the USB host side can be a realistic attacker-controlled peer once connected. Not awarded: * No privilege escalation bonus. The patch shows an out-of-bounds read and kernel memory disclosure, not UAF reclaim, controlled overwrite, callback control, or type confusion. * No integrity impact bonus. The described primitive copies kernel memory out. It does not write attacker-controlled data into kernel objects or shared pages. * No strong generic memory corruption bonus. This is best classified as OOB read / info leak, not OOB write or heap overwrite. ## 3. Reachability analysis The bug can be triggered by a malicious USB host sending malformed NCM NTBs to a Linux device acting as a USB gadget. No local account or Linux privileges on the victim are needed if the attacker controls the host side of the USB connection. Namespaces and containers are not the main factor here because the vulnerable input arrives through the USB gadget function rather than a local userspace API. The path is not broadly enabled on typical general-purpose servers, but it is realistic on devices that expose USB gadget networking, such as embedded systems, development boards, appliances, phones, or USB-connected test setups. ## 4. Severity interpretation This is more than an ordinary Moderate because the patch and commit message describe a concrete kernel out-of-bounds read with possible kernel memory disclosure into a network skb. It does not currently look like an Important-class LPE because there is no write primitive, UAF reuse, object replacement, or control-flow impact shown. Realistically, the strongest demonstrated impact is confidentiality loss from kernel memory exposure, with possible DoS. The paranoid score keeps it in Actionable Moderate territory because externally supplied protocol input can trigger a real memory disclosure primitive. ## 5. One-sentence report phrase A malicious USB host can craft NCM NTB headers with invalid block or datagram bounds so that `ncm_unwrap_ntb()` copies adjacent kernel memory into a network skb, causing kernel memory disclosure and possible DoS on USB gadget devices exposing f_ncm. ## 6. Manual review recommendation MANUAL CHECK REQUIRED This should not be auto-closed because the patch explicitly describes copying adjacent kernel memory into an skb, which is a concrete confidentiality primitive from externally supplied protocol data. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: usb: gadget: f_ncm: validate datagram bounds in ncm_unwrap_ntb() Commit: e07751d0527ccc2a1c32eb0b0b7da3b4b9b5381f Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e07751d0527ccc2a1c32eb0b0b7da3b4b9b5381f Commit description: When unpacking host-supplied NTBs, ncm_unwrap_ntb() checks datagram length against frame_max but does not verify that the datagram fits within the declared block length. Additionally, when decoding multiple NTBs from a single socket buffer, subsequent block lengths are not checked against the actual remaining buffer data. With these checks missing, a malicious USB host can specify datagram offsets and lengths that point beyond the block, or supply secondary NTB headers declaring lengths larger than the buffer. skb_put_data() then copies adjacent kernel memory from skb_shared_info into the network skb. Fix this by verifying that sufficient buffer space remains for the NTB header before parsing, handling zero-length block declarations, ensuring that block lengths never exceed the remaining buffer space, and verifying that each datagram payload stays strictly within the block boundary. Fixes: 427694c ("usb: gadget: ncm: Handle decoding of multiple NTB's in unwrap call") Fixes: 2b74b0a ("USB: gadget: f_ncm: add bounds checks to ncm_unwrap_ntb()") Cc: stable Assisted-by: Jetski:Gemini-2.5-Pro Signed-off-by: Sonali Pradhan Link: https://patch.msgid.link/20260703083725.1903850-1-sonalipradhan@google.com Signed-off-by: Greg Kroah-Hartman Changed files: drivers/usb/gadget/function/f_ncm.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=e07751d0527ccc2a1c32eb0b0b7da3b4b9b5381f ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68368 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68368 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:H/I:N/A:L The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H The Best / paranoid CVSS score: 8.1 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: 4 Paranoid ActionableScore: 5 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).