From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-97594][MODERATE 7.0] landlock: Fix use-after-free of the source's parent directory [ Upstream Date: Fri, 25 Sep 2026 14:18:28 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-97594 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 379efd2ce8b26fd35feb13ccc2f671ff105a5052 List-Id: CVE: CVE-2026-97594 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: landlock: Fix use-after-free of the source's parent directory [ Upstream Commit: 379efd2ce8b26fd35feb13ccc2f671ff105a5052 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=379efd2ce8b26fd35feb13ccc2f671ff105a5052 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97594 Analysis date: Fri, 25 Sep 2026 14:18:28 -0400 ActionableScore: 5 ActionableScore lower bound: unknown Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-97594 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97594 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-2026-97594 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-97594 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-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A race condition in Landlock current_check_refer_path can cause a use after free because the source dentry parent is accessed without a stable reference while concurrent rename and rmdir operations can reparent and free that directory. A local process in a Landlock domain with filesystem access rights can trigger the condition by racing linkat with rename and rmdir operations. For the CVSS the PR:L because an attacker needs local code execution and control of filesystem operations, but does not normally need administrative privileges. The issue is not network reachable. The confirmed impact is a local kernel crash and denial of service. The use after free read creates a plausible but unproven risk of limited confidentiality or integrity impact, so manual review is required.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) YES READ DANGER RACE UAF LINUS KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO 1. ActionableScore * Raw conservative score: 5 * Conservative score: 5 * Raw paranoid score: 5 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: 2. Signal breakdown * +2 Real UAF / active lifetime violation. `old_dentry->d_parent` can be detached by concurrent `rename`, then the former parent can be removed and freed after RCU processing while `current_check_refer_path` still dereferences it. KASAN confirms `slab-use-after-free` in `collect_domain_accesses`. * +1 Local unprivileged trigger. Landlock is intended to allow a process to sandbox itself without host-administrator authority. The supplied context states that a process in a Landlock domain with filesystem access rights can trigger the race through `linkat`, `rename`, and `rmdir`. * +1 Attacker-influenced active-object lifetime manipulation. The attacker can repeatedly drive the relevant namespace lifetime transition through filesystem operations that reparent and remove directories. This is more than a passive one-time teardown event. * +1 Reliable kernel crash / strong DoS. The supplied KASAN trace establishes a stale dentry dereference in the Landlock filesystem-access path. A production kernel may Oops, panic depending on configuration, or otherwise suffer local denial of service. * No hard-race penalty. This is a race, but the attacker can repeatedly execute the participating `linkat`, `rename`, and `rmdir` operations. The supplied reproducer description does not establish an externally uncontrollable or one-shot timing condition. * No controlled reclaim or controlled replacement bonus. The patch establishes use of a freed dentry, but does not establish that an attacker can reclaim the exact slab slot with attacker-shaped contents. * No arbitrary write bonus. The demonstrated stale operation is a read and hierarchy walk. No stale write, directed write, refcount mutation, callback dispatch, or function-pointer influence is shown. * No confidentiality or integrity bonus. A stale dentry read alone does not establish a user-visible disclosure path or unauthorized modification. * No extra availability point. The confirmed crash or fault consequence is counted once and is not double-counted as a separate availability effect. * No concrete repeated release/refcount signal. The new `dput(old_parent)` calls balance the newly acquired `dget` or `dget_parent` reference. The vulnerable path is a stale dereference, not a second lifetime-mutating operation on an already released exact reference. 3. Reachability analysis The evaluated attacker is an ordinary local process, not a remote peer and not necessarily a host administrator. Landlock rulesets can normally be created by an unprivileged process for its own confinement when the process has `no_new_privs`, and the relevant filesystem operations can be performed against files and directories the process can manage. The complete trigger requires entering a Landlock domain that handles at least one filesystem access right, then racing `linkat` against `rename` and `rmdir`. The supplied commit explicitly describes this attacker-controlled operation sequence. No host-only device, boot setting, special hardware, privileged network setup, or separate administrator-created runtime object is identified. Namespace-scoped privilege is not material to the conclusion. The relevant path is local filesystem and Landlock processing, and the supplied evidence supports ordinary local reachability rather than a capability restricted to a user or network namespace. The issue is not directly network reachable. A remote attacker would need an unrelated mechanism to cause a local process to execute the relevant filesystem-operation sequence. 4. Primitive and severity interpretation The exact primitive is a real slab use-after-free of an active filesystem `dentry` object. The former source-parent dentry is selected without a stable reference, then passed to `collect_domain_accesses` for Landlock hierarchy and access-right processing and may also be used by synchronous audit logging. Concurrent rename and removal can free the original parent before these uses complete. This is an active structured-object UAF rather than fixed stale DMA or driver storage. It is also not merely a cleanup or destructor dereference. The stale dentry is consumed during active Landlock filesystem authorization processing. The attacker can repeatedly induce the parent reparenting and removal transition, but controlled replacement of the freed dentry and attacker-controlled post-free field consumption are not established. The primitive is therefore CLASS_B. The demonstrated practical consequence is local kernel denial of service. A stronger confidentiality, integrity, or privilege-escalation consequence is not established by the patch alone. Nevertheless, a local attacker-controlled UAF in active filesystem security processing has unresolved exploitation relevance beyond an ordinary invalid NULL dereference. This supports ImportantCandidate=YES and ManualReview=REQUIRED. AutoDowngradeAllowed=NO because automatically closing the issue as an ordinary crash-only filesystem race would discard a concrete local active-object lifetime violation. The lack of demonstrated controlled reclaim prevents classification as CLASS_A and prevents an Important score of 7 or higher on current evidence. Likely operational severity is Actionable Moderate. It should be patched with normal kernel-security priority and manually reviewed for allocator reuse and Landlock dentry-walk behavior on affected kernel configurations. 5. One-sentence report phrase A local attacker in a Landlock filesystem domain can race linkat, rename, and rmdir operations to dereference a freed source-parent dentry during Landlock access checks, causing kernel denial of service and requiring manual review for unresolved use-after-free exploitation potential. 6. Manual review recommendation MANUAL CHECK REQUIRED A concrete locally reachable slab use-after-free is confirmed by KASAN in an active Landlock filesystem authorization path. Controlled reclaim, disclosure, arbitrary write, and privilege escalation are not demonstrated, but the active structured-object lifetime violation should not be automatically downgraded. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: landlock: Fix use-after-free of the source's parent directory [ Upstream Commit: 379efd2ce8b26fd35feb13ccc2f671ff105a5052 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=379efd2ce8b26fd35feb13ccc2f671ff105a5052 Changed files: security/landlock/fs.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=379efd2ce8b26fd35feb13ccc2f671ff105a5052 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-97594 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97594 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:L/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: unknown 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: YES 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).