From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80572][MODERATE 7.0] Input: byd - synchronize timer deletion before freeing private data Date: Wed, 26 Aug 2026 12:14:38 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80572 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: 8dbfd8e32a13e116790780ed0be82b5a05eb9916 List-Id: CVE: CVE-2026-80572 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: Input: byd - synchronize timer deletion before freeing private data Commit: 8dbfd8e32a13e116790780ed0be82b5a05eb9916 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8dbfd8e32a13e116790780ed0be82b5a05eb9916 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80572 Analysis date: Wed, 26 Aug 2026 12:14:38 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A race in the Input byd driver disconnect path allows a timer callback to access freed private data after `timer_delete()`, creating a local UAF condition that is most realistically a kernel crash risk but should receive manual review for possible privilege escalation impact. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80572 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80572 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-2026-80572 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:H/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in the Input byd mouse driver can occur during disconnect because timer_delete does not wait for an already running byd_clear_touch callback. The callback can dereference the driver private data and the related psmouse pointer after byd_disconnect has freed that private data, which creates a kernel use-after-free condition. The realistic impact is at least a local denial of service via kernel crash because the race happens on the disconnect path and requires a narrow timing window. For the CVSS the PR:L is used in the paranoid score because a local user with delegated device management, reduced root, or access to driver unbind paths could potentially trigger disconnect while input activity keeps the timer active. The issue is not network reachable and normally applies only to systems using the byd psmouse driver. Impact may include privilege escalation in the worst case because the bug class is UAF after kfree, so this should not be treated as DoS only without manual review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) YES INIT SIMPLEFIX TIMER LINUS INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Triggered signals: * Memory corruption, weak primitive: +1 The patch fixes a timer callback race where `byd_clear_touch()` can dereference freed `byd_data`. This is a real UAF, but the patch does not show attacker controlled reclaim, overwrite, type confusion, or object replacement. * Real lifetime corruption: +1 `timer_delete()` does not wait for an already running callback, and the freed private data can remain reachable by the timer callback. * Reliable kernel crash / strong DoS: +1 A stale timer callback dereferencing freed driver private data can plausibly crash the kernel. * Privileged kernel/device-management lifetime path: +1 in paranoid scoring The bug is in input driver disconnect cleanup and object lifetime handling. * Hard or unreliable race / special timing required: -1 The issue requires overlap between disconnect, timer callback execution, and possibly timer rearm. * Requires admin/root/device-management control in typical deployments: -2 for conservative scoring Triggering `byd_disconnect()` normally requires device removal, driver unbind, module unload, suspend teardown, or similar privileged or physical/device-management conditions. Paranoid adjustment: * The full conservative privilege penalty is relaxed for paranoid scoring because delegated device management, reduced root, containerized service control, or physical hotplug style environments may lower practical trigger requirements. * The score is capped at 5 under the Race-UAF downgrade rule because there is no demonstrated reclaim, write-after-free, type confusion, callback target control, or refcount takeover. ## 3. Reachability analysis The bug is local and not network reachable. A realistic trigger normally requires the affected BYD psmouse driver to be in use and a disconnect or teardown path to run while the timer callback or byte processing path is active. In ordinary deployments, causing this disconnect path is usually privileged or tied to physical/device-management events. Namespaces do not normally make PS/2 mouse driver teardown available to an unprivileged user, but delegated device control or reduced-privilege service accounts could make the paranoid PR:L interpretation defensible. Call-site confidence: high. The provided patch directly shows the vulnerable lifetime sequence in `byd_disconnect()`, replacing `timer_delete()` with `timer_shutdown_sync()` immediately before `kfree()`. ## 4. Severity interpretation This behaves like an actionable Moderate kernel lifetime bug, not an ordinary low-risk cleanup. The theoretical risk is higher than pure DoS because the bug class is UAF after `kfree()`. The realistic evidence supports local kernel crash more strongly than privilege escalation, because no controlled reclaim, overwrite, type confusion, or attacker-controlled callback target is shown. Therefore, it should not be auto-closed, but it is weaker than a strong Important candidate. ## 5. One-sentence report phrase A race in the Input byd driver disconnect path allows a timer callback to access freed private data after `timer_delete()`, creating a local UAF condition that is most realistically a kernel crash risk but should receive manual review for possible privilege escalation impact. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a real kernel UAF/lifetime race fixed by switching to `timer_shutdown_sync()`. Even though practical exploitation appears constrained and likely DoS-only, UAF after `kfree()` in a driver teardown path should not be auto-closed without manual review. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: Input: byd - synchronize timer deletion before freeing private data Commit: 8dbfd8e32a13e116790780ed0be82b5a05eb9916 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8dbfd8e32a13e116790780ed0be82b5a05eb9916 Commit description: byd_disconnect() uses timer_delete() before freeing the driver's private data. This does not wait for a running byd_clear_touch() callback, which dereferences the private data and its psmouse pointer. A callback racing with disconnect can therefore access the private data after it has been freed. The timer can also still be re-armed by byd_process_byte() while the disconnect is in progress. Use timer_shutdown_sync() before freeing the private data: it waits for a running callback and turns any later re-arm attempt into a no-op. Fixes: 2d5f561 ("Input: byd - enable absolute mode") Cc: stable@vger.kernel.org Signed-off-by: Linmao Li Link: https://patch.msgid.link/20260720061259.1601281-1-lilinmao@kylinos.cn Signed-off-by: Dmitry Torokhov Signed-off-by: Greg Kroah-Hartman Changed files: drivers/input/mouse/byd.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=8dbfd8e32a13e116790780ed0be82b5a05eb9916 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80572 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80572 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:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 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: 3 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: NO 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).