From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98439][MODERATE 7.0] smb/server: cancel async requests when closing connection [ Upstream Date: Mon, 19 Oct 2026 05:01:29 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98439 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: 4 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: 0947087678f465b64eba2acebe808d5c6cfea036 List-Id: CVE: CVE-2026-98439 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: smb/server: cancel async requests when closing connection [ Upstream Commit: 0947087678f465b64eba2acebe808d5c6cfea036 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0947087678f465b64eba2acebe808d5c6cfea036 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98439 Analysis date: Mon, 19 Oct 2026 05:01:29 -0400 ActionableScore: 4 ActionableScore lower bound: 3 Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: A remote SMB client may leave an asynchronous ksmbd request pending while closing its connection, preventing reference-count completion and potentially accumulating blocked connections and retained server resources. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98439 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98439 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-2026-98439 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98439 CHECK WITH IMPACT FROM ORIG NN NONE | AEGIS IMPACT MODERATE AEGIS_AS=2 LEGACY=MODERATE_KPANIC RESULT=DIFF (final Legacy and Aegis differ; FINAL: MODERATE_KPANIC, Aegis: MODERATE) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';**CWE-400;*CWE-772;CWE-404;Other CVSS 'AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '7.5';DESCR 'An active asynchronous SMB request can remain pending when a ksmbd connection is closed. The request can retain a connection reference while the connection handler waits for its reference count to reach zero, which can prevent the connection from being released. A remote SMB client may trigger the condition by starting a long lived asynchronous operation and then closing the connection. For the CVSS the PR:N value is used for the paranoid score because guest or anonymous SMB configurations may allow the required request sequence without attacker credentials. The base score uses PR:L because authenticated share access is the more typical deployment requirement. A single trigger is expected to stall one connection, while repeated triggers may accumulate retained connections and cause service resource exhaustion. Impact is denial of service. No supported memory corruption, information disclosure, or integrity modification primitive is visible in the affected path. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 7.5 and the production ActionableScore returned 4 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 ActionableScore threshold rule was applied. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4. The independent weaker Aegis shadow evaluated CVSS 4.3 and ActionableScore 2 with primitive class CLASS_C and manual review RECOMMENDED. Its independently reconciled impact was MODERATE. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) MAYBE REMOTE LOCK DISK SKIP KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=3 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: 3 * Conservative score: 3 * Raw paranoid score: 4 * Paranoid score: 4 * No floor or cap was applied. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown Conservative signals: * +2 Remote reachability. A network SMB client controls the connection lifecycle and can leave an asynchronous request pending before closing the connection. * +1 Concrete resource and reference retention. The pending request prevents `conn->r_count` from reaching zero, leaving the connection handler blocked and connection resources unreleased. Paranoid signal: * +1 Potential repeated resource exhaustion. Repeating the sequence across multiple connections could accumulate blocked handlers and retained connection resources, although host-wide exhaustion and applicable connection limits are not demonstrated. Not awarded: * No UAF, OOB access, double release, active-state corruption, or attacker-controlled write is established. * No crash point, panic, arbitrary write, disclosure, authorization bypass, or privilege-escalation primitive is shown. * No additional availability point is awarded conservatively because the demonstrated effect is limited to failure to close an affected connection. * No race penalty is applied. The defect is an ordered lifecycle and cancellation failure rather than an established narrow timing race. * B5-R does not apply because there is no heap OOB write or retry-accumulated offset. * B3-PENDING does not apply because no shared-backing write exists. * B4-PENDING does not apply because no DENY-to-ALLOW authorization decision changes. * V33 and V34 do not apply because no attacker-influenced active structured-state corruption or downstream metadata consumption is present. 3. Reachability analysis The evaluated attacker is a remote SMB client connected to an enabled ksmbd service. Host UID 0 and host-administrator capabilities are not required to close a client connection or submit protocol requests. The exact asynchronous operation and its authentication or share-access requirements are not shown, so anonymous triggering is unresolved, but even an authenticated SMB account remains below host-admin privilege. The host administrator must initially configure and expose ksmbd, but this is service deployment rather than host-admin privilege required for each trigger. No namespace capability, special hardware, boot option, or local control-plane operation is implicated. The client can repeat connection creation and closure, but the number of requests that remain pending indefinitely and the effectiveness of server-side limits are not established. 4. Primitive and severity interpretation The exact primitive is failure to cancel an active asynchronous request before waiting for all connection references to disappear. The request remains valid and retains its reference, so this is resource retention rather than post-lifetime access. There is no stale freed object, repeated lifetime mutation, corrupted structured state, or secondary consumer of corrupted data. The demonstrated consequence is that an affected connection cannot finish closing. The paranoid consequence is service degradation through accumulation of multiple retained connections, but host-wide exhaustion is unresolved. This is CLASS_C because the demonstrated behavior is lifecycle-related DoS without an independently useful corruption primitive. ImportantCandidate is NO because there is no memory-corruption, ownership, authorization, or cross-boundary integrity mechanism. AutoDowngradeAllowed is YES because manual analysis is not needed to resolve an outstanding exploitation primitive, although operational review of remote repeatability is still recommended. 5. One-sentence report phrase A remote SMB client may leave an asynchronous ksmbd request pending while closing its connection, preventing reference-count completion and potentially accumulating blocked connections and retained server resources. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Confirm which SMB asynchronous commands reach this path, whether guest sessions can invoke them, whether waits can remain indefinite, and whether repeated connections can bypass limits and cause host-wide service exhaustion. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: smb/server: cancel async requests when closing connection [ Upstream Commit: 0947087678f465b64eba2acebe808d5c6cfea036 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0947087678f465b64eba2acebe808d5c6cfea036 Changed files: fs/smb/server/connection.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=0947087678f465b64eba2acebe808d5c6cfea036 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98439 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98439 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:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 7.5 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: 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: 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).