From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-90173][MODERATE 7.0] smb: smbdirect: free completion queues with ib_free_cq() [ Upstream Date: Fri, 18 Sep 2026 02:17:37 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-90173 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: 8a953b1a47fffb71e70767bc1e914401e3c2f27f List-Id: CVE: CVE-2026-90173 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: smb: smbdirect: free completion queues with ib_free_cq() [ Upstream Commit: 8a953b1a47fffb71e70767bc1e914401e3c2f27f Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8a953b1a47fffb71e70767bc1e914401e3c2f27f Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90173 Analysis date: Fri, 18 Sep 2026 02:17:37 -0400 ActionableScore: 5 ActionableScore lower bound: unknown Actionable bucket: Actionable Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90173 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90173 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-90173 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-90173 CHECK WITH IMPACT FROM ORIG NN NONE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-672;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'A use after free can occur in the SMB Direct teardown path because completion queues created with workqueue based polling are freed while ib_cq_poll_work can still be pending or requeued. A late RDMA completion after rdma_destroy_qp can schedule work against the freed CQ, leading to an invalid kernel memory access and a kernel crash. The KASAN trace confirms a slab use after free in ib_cq_poll_work followed by a fault in rxe_req_notify_cq. For the CVSS the PR:N value is used because a remote SMB Direct peer may influence connection teardown and late completion processing without local privileges on the target. AV:A and AC:H are used because the attacker normally needs access to the same RDMA or Soft RoCE network and must trigger a timing dependent race involving a late provider completion. The demonstrated impact is denial of service. Because this is a confirmed kernel heap UAF, object reuse may theoretically create confidentiality or integrity impact and requires manual security review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate (with actual score 5) SKIP CVE-2026-90173 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE REMOTE READ OOB DANGER DISK INIT UAF SKIP KERNEL_PANIC_PLUS_UAF HARDWARE LINUS KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 5 * Conservative score: 5 * Raw paranoid score: 5 * Paranoid score: 5 * No floor or cap changed either score. * Final recommended bucket: **Actionable Moderate**:: 2. Signal breakdown * +2 Real UAF / active lifetime violation. `ib_destroy_cq()` frees the CQ while pending or newly requeued `ib_cq_poll_work` can still dereference it. KASAN directly confirms a slab use-after-free. * +2 Direct network reachability. An SMB Direct peer on the reachable RDMA or Soft-RoCE fabric can influence connection establishment, teardown, RNR processing, and the late completion that enters the vulnerable path. * +1 Reliable kernel crash / strong DoS. The supplied trace shows a post-free read followed by a supervisor page fault and kernel Oops. * No race penalty. The ordering is asynchronous, but the evidence does not establish a narrow, one-shot, externally uncontrollable race. Connection attempts can be repeated. * No additional Availability point. The Oops is the same consequence already counted as strong DoS. * No structured stale-object leverage point. The CQ is structured and provider operations consume it, but attacker-controlled reclaim, replacement contents, or useful post-free field control is not established. * No active-lifetime manipulation point. The peer influences connection lifetime, but the evidence does not establish meaningful control over CQ reuse or post-free state. * Controlled reclaim, arbitrary or directed write, information disclosure, callback hijacking, refcount takeover, and privilege escalation are not demonstrated. * No Confidentiality or Integrity points are awarded from the paranoid CVSS alone. * No concrete repeated release/refcount operation exists. The bug is stale asynchronous work after one CQ free, not a second `put`, `free`, or refcount mutation on the same dangling reference. * The repeated-release signal and repeated-refcount paranoid point are therefore withheld. FLOOR 5 was not applied because the raw score already equals 5 and the repeated-release condition does not exist. 3. Reachability analysis The evaluated attacker is a remote SMB Direct peer with access to the target RDMA or Soft-RoCE fabric. The call trace connects remote connection acceptance and `rxe_receiver()` processing to CQ work creation, while connection release frees the CQ. No local account, capability, or host-admin privilege is required once the KSMBD SMB Direct listener and RDMA transport are exposed. Therefore `HostAdminRequired=NO`. Administrative deployment is prior setup, but it is not an attacker privilege needed for each trigger. This is not a namespace-capability attack, so `NamespaceScopedPrivilege=NO`. Special physical RDMA hardware is not mandatory because the demonstrated path uses Soft-RoCE. The complete external packet sequence is not shown, but connection and transport errors can plausibly be repeated. The evidence does not justify a hard-race penalty. 4. Primitive and severity interpretation The primitive is a concrete asynchronous post-teardown UAF of an RDMA completion queue. The CQ is an active structured kernel object rather than a passive buffer, and stale work enters CQ polling and provider notification logic. The stale access occurs in teardown-related asynchronous processing. It is not a concrete double release or refcount mutation. The first and only visible lifetime operation frees the CQ, after which queued work reads and processes the stale object. This is CLASS_B because a real kernel lifetime violation is demonstrated. The established consequence is host kernel Oops and denial of service. A stronger result would require evidence of attacker-influenced reclaim, replacement contents, callback selection, or a useful write or disclosure primitive. `ImportantCandidate=NO` because the supplied evidence supports a constrained crash-oriented UAF but not meaningful exploitation leverage beyond the stale CQ processing. `AutoDowngradeAllowed=YES` because no unresolved controlled corruption, repeated lifetime mutation, or security-boundary bypass is established. Operationally, this is an Actionable Moderate issue due to network-adjacent reachability and a confirmed kernel UAF. 5. One-sentence report phrase A remote SMB Direct peer on an accessible RDMA or Soft-RoCE fabric may trigger asynchronous polling of a freed completion queue, causing a confirmed kernel use-after-free and host denial of service. 6. Manual review recommendation MANUAL CHECK RECOMMENDED Review whether practical traffic can reliably control teardown timing and whether CQ slab reclaim can influence fields consumed by `ib_cq_poll_work`, but current evidence establishes only a crash-oriented stale-object path. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: smb: smbdirect: free completion queues with ib_free_cq() [ Upstream Commit: 8a953b1a47fffb71e70767bc1e914401e3c2f27f Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8a953b1a47fffb71e70767bc1e914401e3c2f27f Changed files: fs/smb/smbdirect/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=8a953b1a47fffb71e70767bc1e914401e3c2f27f ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90173 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90173 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:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/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: 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).