From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-92495][MODERATE 7.0] RDMA/bnxt_re: Clear VM_MAYWRITE on DBR/toggle page mmap [ Upstream Date: Fri, 18 Sep 2026 06:16:03 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-92495 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: 4 X-AL-KERNEL-Commit: 5361fb1e5bc246f9a2c0721543f72c8dac200769 List-Id: CVE: CVE-2026-92495 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: RDMA/bnxt_re: Clear VM_MAYWRITE on DBR/toggle page mmap [ Upstream Commit: 5361fb1e5bc246f9a2c0721543f72c8dac200769 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5361fb1e5bc246f9a2c0721543f72c8dac200769 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-92495 Analysis date: Fri, 18 Sep 2026 06:16:03 -0400 ActionableScore: 5 ActionableScore lower bound: 4 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-2026-92495 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-92495 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-2026-92495 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-92495 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H';CWE-732;CWE-284;CWE-668;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '6.1';DESCR 'The bnxt_re RDMA driver rejected writable mmap requests for DBR and toggle pages, but a read-only mapping could still retain VM_MAYWRITE and later be upgraded with mprotect(PROT_WRITE). This bypasses the driver policy that these pages are not expected to be written from userspace and may allow a local RDMA user to modify device related shared state. For the CVSS the PR:L is used because an attacker needs local access to the RDMA userspace interface or an allowed uverbs context, but does not need full administrator privileges in deployments where RDMA device access is delegated. The issue is not directly network reachable and is triggered through a local mmap plus protection change path rather than packet traffic. Impact is primarily integrity policy bypass and denial of service risk for the affected RDMA context or device, with no clear evidence of arbitrary kernel memory write or privilege escalation from the patch alone.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) YES READ INIT SIMPLEFIX NETWORK LINUS KPANIC INCREASED_TO_MODERATE7_FROM_MODERATE_BASED_ON_GUESSCVSS YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 PrimitiveClass=CLASS_A RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO 1. ActionableScore * Raw conservative score: 4 * Conservative score: 4 * Raw paranoid score: 5 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: No floor or cap changed the score. 2. Signal breakdown Conservative positive signals: * +2 Concrete authorization decision bypass. `bnxt_re_mmap()` rejects `VM_WRITE` for `DBR_PAGE` and `TOGGLE_PAGE`, but failure to clear `VM_MAYWRITE` lets a read-only mapping later become writable via `mprotect(PROT_WRITE)`. * +1 Integrity plausible. The attacker can obtain write access to pages that the driver explicitly treats as not writable from userspace, allowing modification of protected device-related shared state. * +1 Local below-host-admin trigger. The operation is reachable by a local RDMA/uverbs user with access to the device context and does not require full host administrator privileges once that access is available. Paranoid additional signal: * +1 Availability risk. Writable access to DBR/toggle pages can plausibly destabilize the RDMA context or device behavior, although a host-wide crash is not directly demonstrated by the patch. Material non-awarded signals: * RealUAF not awarded. No stale pointer, post-free use, RCU lifetime bug, or double release is established. * Controlled kernel memory corruption not awarded. The patch shows writable access to driver/device mapped pages, not arbitrary kernel memory write. * Strong LPE not awarded. No credential overwrite, arbitrary write, controlled reclaim, callback control, or demonstrated privilege escalation is shown. * Remote reachability not awarded. The trigger is local mmap plus mprotect through the RDMA userspace interface, not packet traffic. * Reliable kernel crash not awarded conservatively. The patch supports policy bypass and possible device/context disruption, but not a demonstrated panic. 3. Reachability analysis The evaluated attacker is a local user or process that can open and use the relevant RDMA userspace interface for the bnxt_re device. The complete trigger is local: create the DBR or toggle page mapping as read-only, then upgrade it with `mprotect(PROT_WRITE)` because `VM_MAYWRITE` was left set. Host administrator privilege is not positively required for the complete security-relevant operation in deployments where RDMA device access is delegated to users or services. This supports `HostAdminRequired=NO`. The evidence does not rely on user or network namespaces, so `NamespaceScopedPrivilege=NO`. There is prior device and driver presence requirement: affected Broadcom bnxt_re RDMA hardware and the RDMA userspace interface must be available. This is hardware-specific but not enough by itself to apply a rare-hardware penalty. No race or special timing is required. 4. Primitive and severity interpretation The exact primitive is a local access-control bypass on mmap protection semantics. The driver blocks writable mappings at mmap time, but because `VM_MAYWRITE` remains set on an initially read-only VMA, later `mprotect(PROT_WRITE)` can bypass that policy. This is not a UAF and not a memory-lifetime bug. It is a security-boundary and permission-bypass issue over driver/device shared pages. The affected storage is active device-related shared state rather than ordinary passive metadata. The demonstrated consequence is unauthorized write access to pages the driver says userspace must not write. The practical impact is integrity policy bypass and possible RDMA context or device denial of service. Privilege escalation is not proven from the patch alone. However, because this is a concrete bypass of a write restriction on device shared pages, automatic downgrade would risk hiding a meaningful boundary issue. Therefore `ImportantCandidate=YES`, `ManualReview=REQUIRED`, and `AutoDowngradeAllowed=NO`. 5. One-sentence report phrase The bnxt_re driver rejected writable DBR and toggle page mmap requests, but a read-only mapping could retain VM_MAYWRITE and later be upgraded with mprotect(PROT_WRITE), allowing a local RDMA user to bypass the intended write restriction on device shared pages. 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a concrete mmap permission bypass that grants write access to driver/device pages that are explicitly intended to be read-only from userspace. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: RDMA/bnxt_re: Clear VM_MAYWRITE on DBR/toggle page mmap [ Upstream Commit: 5361fb1e5bc246f9a2c0721543f72c8dac200769 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5361fb1e5bc246f9a2c0721543f72c8dac200769 Changed files: drivers/infiniband/hw/bnxt_re/ib_verbs.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=5361fb1e5bc246f9a2c0721543f72c8dac200769 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-92495 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-92495 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:L/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H The Best / paranoid CVSS score: 6.1 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: 4 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).