From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74379][LOW] dax/kmem: account for partial discontiguous resource upon removal [ Upstream Date: Sun, 16 Aug 2026 07:00:33 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74379 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 1 X-AL-KERNEL-ActionableScore-Lower: 0 X-AL-KERNEL-Commit: ef4fc53898bd6c4d0119cc6d419ebef7f2560f31 List-Id: CVE: CVE-2026-74379 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: dax/kmem: account for partial discontiguous resource upon removal [ Upstream Commit: ef4fc53898bd6c4d0119cc6d419ebef7f2560f31 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ef4fc53898bd6c4d0119cc6d419ebef7f2560f31 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74379 Analysis date: Sun, 16 Aug 2026 07:00:33 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: A NULL pointer dereference in the dax/kmem remove path can occur after a partially successful discontiguous resource probe, causing a local privileged kernel crash during device removal with no evident privilege escalation primitive. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74379 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74379 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: LOW 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-2026-74379 LOW 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:N/I:N/A:H';**CWE-476;CWE-703;CWE-754;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'A NULL pointer dereference can occur in the dax kmem remove path after a partially successful probe of a discontiguous device resource. Some ranges may be skipped during probe and leave data res i unset, but dev_dax_kmem_remove can still iterate over those ranges and later attempt resource cleanup on a NULL pointer. The practical impact is a local denial of service through a kernel crash during DAX kmem device removal. For the CVSS the PR:L is used in the paranoid score to cover environments where a delegated local management process can trigger DAX device remove paths, while typical deployments require administrator level device control. The issue is not network reachable and requires local device management or hardware specific hotplug conditions. No credible privilege escalation or information disclosure primitive is visible from the code path.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) YES SIMPLEFIX DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ActionableScoreLower=0 ## 1. ActionableScore * Conservative score: 0 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown Conservative signals: * Reliable kernel crash / strong DoS: +1. The patch prevents cleanup on a NULL resource pointer in `dev_dax_kmem_remove()`, which can plausibly crash the kernel. * Requires admin/root/CAP_* in typical deployments: -2. Triggering this path normally requires privileged DAX/kmem device management or device removal. * Rare AND difficult-to-reach subsystem/configuration: -1. The issue requires DAX/kmem, discontiguous resources, partial probe success, and later removal. * Physical-only or rare hardware-only condition: -2. Practical triggering depends on device/resource topology and memory hotplug style conditions. Conservative total is clamped to 0. Paranoid adjustment: * Use only a reduced privilege penalty in environments where DAX device removal is delegated to a local management service or reduced-capability operator. * This gives a paranoid score of 1, but still no memory corruption, no LPE primitive, and no network exposure. ## 3. Reachability analysis The bug is locally reachable through DAX/kmem device lifecycle handling, especially after a partially successful probe where some ranges were not actually added. In typical deployments, creating, probing, removing, or hot-unplugging such devices is administrator-controlled and not available to an ordinary local user. Namespaces and containers generally do not make this path unprivileged. A container would need delegated access to relevant device-management or memory-hotplug controls, which is not a normal default configuration. The affected path is not network reachable. Realistic exploitation requires a specific DAX/kmem setup, discontiguous resource handling, a partial probe failure, and a later remove path. Call-site confidence: high. The relevant remove path and NULL check are visible in the patch context. ## 4. Severity interpretation This behaves like an ordinary Moderate or Low-like kernel DoS issue, not an Important-class vulnerability. The failure mode is a NULL pointer cleanup path after inconsistent resource accounting. There is no evidence of UAF, double free, OOB write, attacker-controlled reclaim, arbitrary write, credential impact, or cross-boundary access. The theoretical impact is kernel crash during privileged device removal. Realistic exploitation evidence supports DoS only, under uncommon local hardware/device-management conditions. ## 5. One-sentence report phrase A NULL pointer dereference in the dax/kmem remove path can occur after a partially successful discontiguous resource probe, causing a local privileged kernel crash during device removal with no evident privilege escalation primitive. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can be auto-closed or handled in deferred mode for security triage because it is a rare, privileged, local DAX/kmem cleanup DoS with no supported memory corruption or privilege escalation path. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: dax/kmem: account for partial discontiguous resource upon removal [ Upstream Commit: ef4fc53898bd6c4d0119cc6d419ebef7f2560f31 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ef4fc53898bd6c4d0119cc6d419ebef7f2560f31 Changed files: drivers/dax/kmem.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=ef4fc53898bd6c4d0119cc6d419ebef7f2560f31 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74379 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74379 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:N/I:N/A:H The Best / paranoid CVSS score: 4.7 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: 0 Paranoid ActionableScore: 1 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: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW 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).