From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64103][MODERATE 7.0] scsi: isci: Fix use-after-free in device removal path Date: Sun, 19 Jul 2026 16:33:24 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64103 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: 1412995e10c74644b47f242aea6e4f3d4180e806 List-Id: CVE: CVE-2026-64103 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: scsi: isci: Fix use-after-free in device removal path Commit: 1412995e10c74644b47f242aea6e4f3d4180e806 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1412995e10c74644b47f242aea6e4f3d4180e806 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64103 Analysis date: Sun, 19 Jul 2026 16:33:24 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A use-after-free in the ISCI SCSI device removal path can allow a stale completion tasklet scheduled by IRQ handlers to run after the host object is torn down, causing at least a local kernel crash and requiring manual review for possible privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64103 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64103 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-2026-64103 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-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A use-after-free can occur in the ISCI SCSI driver removal path because completion_tasklet may remain queued while the host object is being torn down. The tasklet is scheduled from MSI-X and legacy interrupt handlers, and killing it before the interrupt source is quiesced is not sufficient because the handler can requeue it. After device remove or driver unload, a stale tasklet callback may dereference the freed ihost object and touch ihost smu_registers, leading at least to a kernel crash and potentially to memory corruption. For the CVSS the PR:L is used in the paranoid score because a reduced capability administrator, service account, or delegated device management context may be able to trigger driver removal or reset without full host control. The issue is local and not network reachable. Impact is at least denial of service, and because the primitive is a UAF in an asynchronous teardown path it should be reviewed for possible privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) YES RACE UAF HARDWARE 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 Conservative scoring: * +2 Generic memory corruption: confirmed UAF class. A stale tasklet can run after `ihost` lifetime ends. * +1 Real lifetime corruption: async tasklet lifetime is not synchronized with host teardown. * +1 Reliable kernel crash / strong DoS: commit describes KASAN analogue and dereference of dead `ihost`. * +1 Privileged kernel/device-management memory corruption path: bug is in SCSI driver teardown with IRQ/tasklet/device state. * -1 Hard or unreliable race / special timing required: requires teardown racing with IRQ-driven tasklet scheduling. * -2 Requires admin/root in typical deployments: device removal, PCI unbind, or module unload usually requires administrative privileges. Paranoid scoring: * Adds +1 Weak LPE concern: stale async callback after free may touch freed/reused driver object state, but no controlled reclaim or write primitive is demonstrated. * Uses reduced privilege penalty rather than full root penalty in some deployments: delegated device management, service accounts, or reduced-capability root can make PR closer to L than H. * Result is capped in the Actionable Moderate range because this is a real UAF, but exploitability beyond DoS is not demonstrated. ## 3. Reachability analysis The realistic trigger is local device removal, driver unload, PCI unbind, or a similar teardown path for ISCI hardware. In ordinary deployments this requires root or equivalent device-management privileges, so the conservative interpretation is privileged local DoS. Namespaces usually do not expose this path to an unprivileged user, but container root, service accounts, or delegated hardware management may reduce the practical privilege requirement. The path is not network reachable. Exposure is limited to systems using the ISCI SCSI driver and relevant Intel C600 storage hardware. ## 4. Severity interpretation This is not an ordinary cleanup bug because the patch fixes a real asynchronous lifetime UAF. Realistic impact is most clearly kernel crash or host instability during device removal. Privilege escalation is not proven because there is no demonstrated attacker-controlled reclaim, object replacement, arbitrary write, or type confusion. However, UAF in an IRQ/tasklet teardown path is historically worth manual review, so this should be treated as Actionable Moderate at minimum, with Important-class consideration only if further analysis shows controllable reuse or write-after-free behavior. ## 5. One-sentence report phrase A use-after-free in the ISCI SCSI device removal path can allow a stale completion tasklet scheduled by IRQ handlers to run after the host object is torn down, causing at least a local kernel crash and requiring manual review for possible privilege escalation. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: confirmed UAF plus async tasklet/IRQ lifetime mismatch. The likely practical impact is DoS, but memory lifetime bugs in driver teardown paths should not be auto-closed without checking whether freed `ihost` memory can be reclaimed or reused in a controlled way. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: scsi: isci: Fix use-after-free in device removal path Commit: 1412995e10c74644b47f242aea6e4f3d4180e806 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1412995e10c74644b47f242aea6e4f3d4180e806 Commit description: The ISCI completion tasklet is initialized in isci_host_alloc() (drivers/scsi/isci/init.c:496) and scheduled from both MSI-X and legacy interrupt handlers (drivers/scsi/isci/host.c:223,613). isci_host_deinit() stops the controller and waits for stop completion, but it never kills completion_tasklet before teardown continues. A top-of-function tasklet_kill() is not sufficient here: interrupts are only disabled when isci_host_stop_complete() runs, so until wait_for_stop() returns the IRQ handlers can still requeue the tasklet. The tasklet callback also re-enables interrupts after draining completions, so killing the tasklet before the source is quiesced leaves the same race open. Once wait_for_stop() returns, no further IRQ-driven scheduling can occur. Kill completion_tasklet there so teardown cannot race a queued tasklet running on a dead ihost. On remove or unload, the stale callback can otherwise dereference ihost and touch ihost->smu_registers after the host lifetime ends. A UML + KASAN analogue reproduced the failure class both with no tasklet_kill() and with tasklet_kill() placed before source quiesce, and stayed clean once the kill happened after quiescing the scheduling source. This mirrors commit f6ab594 ("scsi: aic94xx: fix use-after-free in device removal path"), but ISCI needs the kill after wait_for_stop(). Fixes: 6f231dd ("isci: Intel(R) C600 Series Chipset Storage Control Unit Driver") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-7 Assisted-by: Codex:gpt-5-4 Signed-off-by: Michael Bommarito Link: https://patch.msgid.link/20260419210420.2134639-1-michael.bommarito@gmail.com Signed-off-by: Martin K. Petersen Signed-off-by: Greg Kroah-Hartman Changed files: drivers/scsi/isci/init.c drivers/scsi/isci/host.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=1412995e10c74644b47f242aea6e4f3d4180e806 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64103 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64103 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).