From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98451][MODERATE REGULAR] smb: client: use finish_no_open() for non-regular inodes [ Upstream Date: Mon, 19 Oct 2026 02:12:35 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98451 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: 3 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: ed03d547598c92a036f20e89156540995cac889a List-Id: CVE: CVE-2026-98451 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: smb: client: use finish_no_open() for non-regular inodes [ Upstream Commit: ed03d547598c92a036f20e89156540995cac889a Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ed03d547598c92a036f20e89156540995cac889a Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98451 Analysis date: Mon, 19 Oct 2026 02:12:35 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: The SMB client can leak cifsFileInfo resources and dentry references when O_CREAT resolves to a non-regular inode, allowing repeated local opens or accesses to attacker-prepared SMB paths to accumulate resources and potentially cause denial of service. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98451 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98451 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-2026-98451 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98451 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE AEGIS_AS=1 LEGACY=MODERATE RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H';*CWE-772;*CWE-401;**CWE-400;CWE-703;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.3';DESCR 'The SMB client atomic open path can attach cifsFileInfo to an existing symlink or another non-regular inode even though such an inode has no matching CIFS release operation. The retained cifsFileInfo keeps a dentry reference and potentially related open resources alive, while FMODE_OPENED also prevents the VFS from continuing normal symlink resolution. A local process can reach the condition by issuing O_CREAT opens for suitable objects on a mounted SMB share. A malicious SMB server may also influence the returned inode type, but exploitation still requires the client or a user to access the prepared path. For the CVSS the PR:N value is used for the paranoid network scenario because the malicious server needs no privileges on the client, while UI:R and AC:H reflect the required client access and repeated accumulation. Impact is resource retention and possible denial of service after sustained abuse. There is no supported UAF, OOB access, arbitrary write, information disclosure, or privilege escalation primitive in this code path. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 5.3 and the production ActionableScore returned 3 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the manual review requirement was applied. ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore threshold rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4. The independent weaker Aegis shadow evaluated CVSS 5.3 and ActionableScore 1 with primitive class CLASS_C and manual review RECOMMENDED. Its independently reconciled impact was MODERATE. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) MAYBE DISK PRINTF-TTY LEAK SERVERTOCLIENT LINUS INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw conservative score: 2 * Conservative score: 2 * Raw paranoid score: 3 * Paranoid score: 3 * No floor or cap was applied. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown Conservative positive signals: * +1 Concrete persistent kernel resource/reference leak. `finish_open()` attaches a `cifsFileInfo`, but symlink inodes have no CIFS release operation, permanently retaining its dentry reference. * +1 Local unprivileged trigger. After an SMB share is mounted and accessible, an ordinary process can issue `O_CREAT` opens against existing non-regular inodes without host-administrator privileges. Additional paranoid signal: * +1 Repeatable resource accumulation concern. Repeated qualifying opens can create additional leaked `cifsFileInfo` and dentry references, making resource exhaustion plausible, although host-wide exhaustion is not demonstrated. Not awarded: * No UAF, OOB access, double release, stale dereference, or memory overwrite is established. * No reliable kernel crash or host-wide exhaustion is demonstrated. * No confidentiality, integrity, authorization-bypass, or privilege-escalation primitive is established. * No direct remote-reachability bonus. A malicious SMB server can influence inode type, but an existing mount and a client-side open operation are still required. * NEW52 B5-R does not apply because there is no heap OOB write or retry-accumulated corrupted-state consumption. * NEW53 B3-PENDING does not apply because no shared-backing write occurs. * NEW54 B4-PENDING does not apply because no mandatory authorization guard changes from DENY to ALLOW. 3. Reachability analysis An ordinary local process with permission to access an already mounted SMB share can trigger the leaking path by opening an existing symlink or another non-regular inode with `O_CREAT`. Creating the mount normally requires prior privileged setup, but triggering the defect after that setup does not require host UID 0 or an administrative capability. A malicious SMB server can prepare or return a qualifying inode type, but it cannot trigger the leak solely through unsolicited network traffic. The client or a local workload must access the path. No namespace-scoped capability is required, and no special hardware, boot option, race, or timing window is involved. 4. Primitive and severity interpretation The exact primitive is a persistent kernel reference and resource leak caused by attaching `cifsFileInfo` to an inode that lacks the matching CIFS release operation. `FMODE_OPENED` also produces incorrect VFS symlink behavior, but this is a semantic lookup failure rather than an authorization bypass. This is not an active-object UAF or repeated lifetime mutation. No object is shown to be freed and subsequently accessed. The demonstrated consequence is retained resources and incorrect open handling. Sustained repetition may cause memory pressure or denial of service, but immediate kernel failure and host-wide exhaustion are unresolved. `PrimitiveClass=CLASS_C` is appropriate because the issue is resource-retention and invalid-state behavior without an independently useful corruption primitive. `ImportantCandidate=NO` because no memory corruption, protected-state modification, or security-boundary bypass is established. `AutoDowngradeAllowed=YES` because the remaining risk is a constrained resource leak that can be handled as Low or Moderate unless deployment-specific testing demonstrates practical host-wide exhaustion. 5. One-sentence report phrase The SMB client can leak cifsFileInfo resources and dentry references when O_CREAT resolves to a non-regular inode, allowing repeated local opens or accesses to attacker-prepared SMB paths to accumulate resources and potentially cause denial of service. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Confirm whether repeated opens produce practically significant unbounded accumulation in the affected deployment and whether an untrusted SMB server can reliably drive a normal client workload through the leaking branch. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: smb: client: use finish_no_open() for non-regular inodes [ Upstream Commit: ed03d547598c92a036f20e89156540995cac889a Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ed03d547598c92a036f20e89156540995cac889a Changed files: fs/smb/client/dir.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=ed03d547598c92a036f20e89156540995cac889a ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98451 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98451 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:L/PR:L/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.3 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: 3 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).