From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74461][MODERATE 7.0] i2c: imx: Cancel hrtimer before clearing slave pointer Date: Sat, 15 Aug 2026 09:55:36 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74461 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: 2 X-AL-KERNEL-Commit: a8a1f9ac3d763e721586f15479ef9140b216ddf3 List-Id: CVE: CVE-2026-74461 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: i2c: imx: Cancel hrtimer before clearing slave pointer Commit: a8a1f9ac3d763e721586f15479ef9140b216ddf3 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a8a1f9ac3d763e721586f15479ef9140b216ddf3 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74461 Analysis date: Sat, 15 Aug 2026 09:55:36 -0400 ActionableScore: 5 ActionableScore lower bound: 2 Actionable bucket: Actionable Moderate under paranoid interpretation / Low to ordinary Moderate under conservative deployment assumptions Manual review required: NO Summary: A race in the i2c imx slave unregister path can leave a pending hrtimer active after the slave pointer lifetime ends, causing a NULL or stale pointer dereference in the timer callback and a local kernel crash, with only weak privilege escalation concern under delegated device access assumptions. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74461 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74461 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-74461 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:L/I:L/A:H';CWE-362;*CWE-416;**CWE-476;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A race in the i2c imx slave unregister path can leave a pending hrtimer active after the slave pointer is cleared. If the timer callback runs later, i2c_imx_slave_finish_op() can call the slave event path with a NULL or stale slave pointer, causing a kernel crash and creating a use-after-free candidate. For the CVSS the PR:L is used for the paranoid score because a local low privilege service or delegated device management context could potentially trigger slave unregister while the timer race is reachable. The issue is not network reachable over IP. External I2C bus activity may help hit the timing window, but exploitation normally requires local device control or physical bus access. Impact is at least local denial of service via kernel crash and in worst case may allow limited confidentiality or integrity impact due to the timer based use-after-free candidate, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate under paranoid interpretation / Low to ordinary Moderate under conservative deployment assumptions (with actual score 4) YES NULLPTR USB UAF TIMER LINUS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate under paranoid interpretation / Low to ordinary Moderate under conservative deployment assumptions**:: ## 2. Signal breakdown Conservative signals: * Memory corruption, weak/indirect corruption candidate: +1 The commit explicitly mentions use-after-free / NULL pointer dereference, but the demonstrated primitive is a timer callback using a NULL or stale slave pointer, not attacker-controlled reclaim or overwrite. * Real lifetime corruption: +1 A pending hrtimer can outlive the valid slave pointer lifetime. * Reliable kernel crash / strong DoS: +1 The expected concrete failure is NULL pointer dereference or stale pointer dereference in kernel timer context. * Hard or unreliable race / special timing required: -1 The bug requires timing between unregister, an interrupt-started hrtimer, and timer callback execution. * Requires admin/root/CAP-level device control in typical deployments: -2 Registering or unregistering I2C slave devices is normally restricted to privileged local code. * Rare hardware / non-default mode: -1 This is specific to the i.MX I2C controller slave-mode path, not a broad default kernel interface. Paranoid additions / interpretation: * Firmware-mediated or external bus influence: +1 External I2C bus activity can help create the interrupt/timer condition, although this is not IP-network reachable. * Weak LPE concern: +1 The stale object is used from an asynchronous timer callback path and may enter the slave event path. This is weaker than a demonstrated reclaim primitive, but enough for manual-review sensitivity. * Privileged kernel/device-management lifetime path: +1 The corruption occurs in a trusted device driver lifetime path involving interrupts, hrtimers, and device unregister state. ## 3. Reachability analysis The realistic trigger requires local control over I2C slave unregister or a privileged service that can manage the affected i.MX I2C controller. In normal deployments this is not reachable by an unprivileged user, and it is not remotely reachable over IP. Containers or delegated device-management services can lower the practical privilege boundary if they expose I2C control to less trusted code. External I2C bus activity may help hit the timing window, but exploitation still depends on local device state changes and specific i.MX slave-mode hardware/configuration. ## 4. Severity interpretation This behaves primarily like a local privileged DoS in conservative scoring. The concrete demonstrated impact is kernel crash through NULL/stale pointer use. The paranoid score treats it as Actionable Moderate because the bug is a real lifetime race in a timer callback path and the commit explicitly identifies a use-after-free candidate. There is not enough evidence for Important-class treatment because no attacker-controlled reclaim, arbitrary write, type confusion, or strong privilege-escalation primitive is shown. ## 5. One-sentence report phrase A race in the i2c imx slave unregister path can leave a pending hrtimer active after the slave pointer lifetime ends, causing a NULL or stale pointer dereference in the timer callback and a local kernel crash, with only weak privilege escalation concern under delegated device access assumptions. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED This should not be auto-closed solely as a NULL dereference because the patch context explicitly includes a timer-based use-after-free candidate, but the review priority is below Important unless a practical reclaim or callback-control primitive is found. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: i2c: imx: Cancel hrtimer before clearing slave pointer Commit: a8a1f9ac3d763e721586f15479ef9140b216ddf3 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a8a1f9ac3d763e721586f15479ef9140b216ddf3 Commit description: In i2c_imx_unreg_slave(), the slave pointer is set to NULL after disabling interrupts. However, a pending interrupt might already have started the hrtimer (i2c_imx_slave_timeout) before the pointer was cleared. If the hrtimer fires after i2c_imx->slave is set to NULL, the timer callback i2c_imx_slave_finish_op() will call i2c_imx_slave_event() with a NULL slave pointer, which results in a use-after-free / NULL pointer dereference. Fix by canceling the hrtimer and waiting for it to complete after disabling interrupts, before clearing the slave pointer. Fixes: f7414cd ("i2c: imx: support slave mode for imx I2C driver") Signed-off-by: Liem Cc: # v5.11+ Acked-by: Carlos Song Reviewed-by: Frank Li Signed-off-by: Andi Shyti Link: https://lore.kernel.org/r/20260629023829.152651-3-liem16213@gmail.com Signed-off-by: Greg Kroah-Hartman Changed files: drivers/i2c/busses/i2c-imx.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=a8a1f9ac3d763e721586f15479ef9140b216ddf3 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74461 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74461 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:L/I:L/A:H The Best / paranoid CVSS score: 5.8 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: 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).