From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74272][MODERATE REGULAR] cxl/region: Resolve region deletion races [ Upstream Date: Sat, 15 Aug 2026 07:45:30 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74272 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 4 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: be44c1c04f85d7b7ac1c597a30b443bbd346acbd List-Id: CVE: CVE-2026-74272 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: cxl/region: Resolve region deletion races [ Upstream Commit: be44c1c04f85d7b7ac1c597a30b443bbd346acbd Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=be44c1c04f85d7b7ac1c597a30b443bbd346acbd Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74272 Analysis date: Sat, 15 Aug 2026 07:45:30 -0400 ActionableScore: 4 ActionableScore lower bound: 2 Actionable bucket: Borderline manual review recommended / Actionable Moderate not established Manual review required: YES Summary: A race in CXL region deletion can let sysfs deletion and root decoder teardown target the same region lifecycle path more than once, creating a privileged local device-management DoS risk and a weak stale-object/UAF concern without a demonstrated privilege-escalation primitive. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74272 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74272 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 REGULAR 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-2026-74272 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW 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-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.8';DESCR 'CXL region deletion has a race where sysfs initiated deletion and root decoder teardown can target the same region object more than once. Multiple deletion paths can leave stale lifecycle state around a kernel device object and may cause warnings, use after free style access, or a crash depending on timing. For the CVSS the PR:L is used for the paranoid score because a delegated host management service or reduced capability admin that can write CXL region sysfs controls may trigger deletion without full host root workflows. The issue is local and control plane only, not network reachable. Impact is at least denial of service and in the paranoid view may include limited confidentiality or integrity impact if stale region object state is later reused.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / Actionable Moderate not established (with actual score 3) YES INIT WARNONLY RACE HARDWARE INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 4 * Final recommended bucket: **Borderline manual review recommended / Actionable Moderate not established**:: ## 2. Signal breakdown Triggered signals: * Real lifetime corruption: +1 Region deletion races can cause the same CXL region lifecycle path to be reached more than once through sysfs deletion and root decoder teardown. * Memory corruption, weak/indirect corruption candidate: +1 The patch prevents stale or duplicate object lifecycle handling around `struct cxl_region`, `device_del()`, devres release, and root decoder teardown. No attacker controlled reclaim, overwrite, callback control, or type confusion is shown. * Privileged kernel/device-management memory corruption path: +1 The affected code is CXL region and root decoder management. It operates on trusted kernel device objects and teardown state. * Availability impact realistic: +1 Duplicate region deletion or teardown races can cause warnings, broken cleanup, and possible device-management disruption. The patch does not show a reliable host-wide panic, so this is not counted as strong DoS. Subtractors: * Hard or unreliable race / special timing required: -1 The issue depends on racing sysfs deletion, repeated deletion, and root decoder teardown. * Requires admin/root/CAP_* in typical deployments: -1 conservative refinement for paranoid score, -2 for lower score CXL region deletion through sysfs is normally administrator controlled. The paranoid score uses -1 because delegated host-management services or reduced-capability admin contexts may have access to these controls without being full host root. Not awarded: * No remote reachable signal. * No strong LPE plausibility. * No strong memory corruption primitive. * No confidentiality or integrity impact in the conservative score. * No Dirty-Pipe-like or shared-page ownership violation. ## 3. Reachability analysis The primary trigger is local CXL sysfs region management, especially deleting the same region concurrently or racing userspace deletion against root decoder teardown. In normal deployments this requires administrative control over CXL device-management interfaces. Namespaces and containers usually do not make this reachable unless CXL sysfs controls are delegated into a management container or exposed to a reduced-privilege service. The affected subsystem is hardware dependent and not default-exposed on systems without CXL devices. There is no realistic network trigger from the patch. Call-site confidence: high. The patch includes the relevant deletion paths, root decoder unregister path, region creation guard, and replacement of devres actions with an xarray protected by `regions_lock`. ## 4. Severity interpretation This behaves more like a borderline Moderate lifecycle race than an Important-class vulnerability on current evidence. Theoretical stale object or UAF-style risk exists because the same region object can be targeted by multiple deletion mechanisms, but the patch does not demonstrate attacker-controlled reuse, write-after-free, callback dispatch, type confusion, or an exploit primitive. The conservative interpretation is low-to-moderate privileged DoS or warning. The paranoid interpretation keeps it for manual review because CXL region objects are privileged device-management objects and duplicate unregister paths can hide subtle lifetime bugs. ## 5. One-sentence report phrase A race in CXL region deletion can let sysfs deletion and root decoder teardown target the same region lifecycle path more than once, creating a privileged local device-management DoS risk and a weak stale-object/UAF concern without a demonstrated privilege-escalation primitive. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is not a clear Important-class issue, but it is a kernel object lifecycle race in CXL teardown code with possible stale region handling. It should not be auto-closed without confirming whether duplicate `device_del()` or devres teardown can lead to UAF, double cleanup, or only a warning. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: cxl/region: Resolve region deletion races [ Upstream Commit: be44c1c04f85d7b7ac1c597a30b443bbd346acbd Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=be44c1c04f85d7b7ac1c597a30b443bbd346acbd Changed files: drivers/cxl/core/core.h drivers/cxl/core/port.c drivers/cxl/core/region.c drivers/cxl/cxl.h 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=be44c1c04f85d7b7ac1c597a30b443bbd346acbd ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74272 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74272 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:L 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: 4 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 REGULAR 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).