From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-68374][MODERATE 7.0] usb: core: sysfs: add lock to bos_descriptors_read() Date: Mon, 10 Aug 2026 16:16:48 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-68374 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: c07caee449c968842a350bfefa049889923b8240 List-Id: CVE: CVE-2026-68374 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: usb: core: sysfs: add lock to bos_descriptors_read() Commit: c07caee449c968842a350bfefa049889923b8240 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c07caee449c968842a350bfefa049889923b8240 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68374 Analysis date: Mon, 10 Aug 2026 16:16:48 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A race in USB core sysfs BOS descriptor reads can use `udev->bos` after it is freed by a concurrent USB reset, allowing a local attacker with access to the sysfs attribute and reset timing to cause a kernel crash and potentially disclose stale kernel heap data. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68374 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68374 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-2026-68374 MODERATE CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:H';*CWE-416;CWE-362;CWE-667;*CWE-200;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '6.3';DESCR 'bos_descriptors_read reads udev bos from a USB sysfs binary attribute without holding the USB device lock. A concurrent USB reset path can free or replace udev bos while the sysfs read path still uses the old pointer, leading to a use after free read when bos desc is dereferenced and copied to the read buffer. This is a local race and requires timing between reading the sysfs BOS descriptors file and a device reset or driver path that calls usb_reset_and_verify_device. For the CVSS the PR:L is used because triggering requires a local process interacting with sysfs and a practical way to cause or race a USB reset path. The issue is not directly network reachable. Impact is at least local denial of service via kernel crash. The worst still defensible impact includes possible confidentiality loss because stale or reused kernel heap data may be copied back through the sysfs read path. Integrity impact is not assigned because the primitive shown by the patch is a stale read rather than a kernel write.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) YES USB UAF HARDWARE LINUS KPANIC NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1 The vulnerable path is a sysfs read handler for USB BOS descriptors. Reading sysfs binary attributes is commonly reachable by local users, although reliably racing a reset may depend on device permissions or driver behavior. * Memory corruption, weak primitive: +1 This is a race-dependent UAF read candidate. The patch prevents `udev->bos` from being used while it may be freed by `usb_reset_and_verify_device()`. No attacker-controlled reclaim, write-after-free, callback dispatch, or type confusion is shown. * Real lifetime corruption: +1 The bug is a real object lifetime issue: `udev->bos` can be freed concurrently while `bos_descriptors_read()` still uses the stale pointer. * Reliable kernel crash / strong DoS: +1 Dereferencing a freed `usb_host_bos` or its `desc` pointer can plausibly lead to kernel Oops, KASAN UAF, or crash. * Confidentiality impact plausible: +1 The stale descriptor data is copied into the sysfs read buffer. If the freed memory is reused before the copy, limited kernel heap disclosure is plausible. Negative signal: * Hard or unreliable race / special timing required: -1 Exploitation requires timing between a local sysfs read and a USB reset path. Paranoid additional signal: * Broad/common subsystem or firmware-mediated external influence: +1 USB core sysfs is broadly present, and `usb_reset_and_verify_device()` is called by many drivers. A malicious or unstable USB device may help create reset timing, although this is not network reachable. Caps applied: * Race-UAF downgrade rule applies. Conservative score capped at 4 and paranoid score capped at 5 because the patch shows stale read/lifetime corruption but not controlled reclaim, write-after-free, type confusion, callback control, or refcount takeover. ## 3. Reachability analysis A local process can read the USB BOS descriptors sysfs attribute. The racing reset side may be triggered by driver behavior, device errors, privileged reset operations, or potentially malicious USB hardware behavior. This is not remotely network reachable. Containers usually do not expose host USB sysfs and device reset control by default, but delegated USB device access can lower practical barriers. The path is common on systems with USB devices, but reliable exploitation depends on hitting a narrow race window. Call-site confidence: high. The patch directly shows the sysfs read path and the commit message identifies the freeing side in `usb_reset_and_verify_device()`. ## 4. Severity interpretation This behaves like an actionable Moderate UAF-read race rather than a clear Important-class LPE. The theoretical memory corruption concern is real because a freed kernel object can be dereferenced. Realistic exploitation evidence is weaker because the visible primitive is stale read and copy, not attacker-controlled reclaim or write. The main practical impacts are local DoS and possible kernel information disclosure. Privilege escalation is not strongly supported by the patch. ## 5. One-sentence report phrase A race in USB core sysfs BOS descriptor reads can use `udev->bos` after it is freed by a concurrent USB reset, allowing a local attacker with access to the sysfs attribute and reset timing to cause a kernel crash and potentially disclose stale kernel heap data. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a race-based UAF read in a common kernel subsystem with plausible DoS and possible information disclosure. It should not be auto-closed, but current evidence does not justify treating it as a strong Important candidate without a demonstrated reclaim or write primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: usb: core: sysfs: add lock to bos_descriptors_read() Commit: c07caee449c968842a350bfefa049889923b8240 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c07caee449c968842a350bfefa049889923b8240 Commit description: Add a lock to the function bos_descriptors_read(). This function accesses udev->bos, which could be simultaneously freed in usb_reset_and_verify_device(), a function that is commonly called in drivers all over the kernel. Assisted-by: gkh_clanker_t1000 Signed-off-by: Griffin Kroah-Hartman Acked-by: Alan Stern Cc: stable Link: https://patch.msgid.link/20260715-usb_core_patches_3-v1-1-53021f5576fd@kroah.com Signed-off-by: Greg Kroah-Hartman Changed files: drivers/usb/core/sysfs.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=c07caee449c968842a350bfefa049889923b8240 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68374 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68374 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:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:H The Best / paranoid CVSS score: 6.3 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).