From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-72500][MODERATE 7.0] RDMA/bnxt_re: Free SRQ toggle page after firmware teardown [ Upstream Date: Sat, 15 Aug 2026 22:16:32 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-72500 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: 7 X-AL-KERNEL-ActionableScore-Lower: 5 X-AL-KERNEL-Commit: 104a7ff382a58a83cae018925e3574c784e8274c List-Id: CVE: CVE-2026-72500 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: RDMA/bnxt_re: Free SRQ toggle page after firmware teardown [ Upstream Commit: 104a7ff382a58a83cae018925e3574c784e8274c Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=104a7ff382a58a83cae018925e3574c784e8274c Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72500 Analysis date: Sat, 15 Aug 2026 22:16:32 -0400 ActionableScore: 7 ActionableScore lower bound: 5 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: A race in the bnxt_re SRQ destroy path can free the SRQ toggle page before firmware teardown completes, allowing an NQ interrupt to write toggle values into freed kernel memory and creating a local write-after-free condition with DoS and possible privilege-escalation concern. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72500 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72500 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-2026-72500 MODERATE CHECK WITH IMPACT FROM ORIG NN IMPORTANT Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-787;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A race in the bnxt_re RDMA SRQ destroy path can free the userspace visible SRQ toggle page before firmware teardown has completed. If an NQ interrupt arrives during bnxt_qplib_destroy_srq(), the driver can write toggle values into an already freed page, creating a use after free memory corruption condition. For the CVSS the PR:L is used because a local process generally needs access to RDMA uverbs or equivalent device permissions to create and destroy SRQs. The issue is not directly network reachable because a remote peer normally cannot destroy the local SRQ, although RDMA activity and device interrupts may influence timing. Impact is at least a local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to memory corruption and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7) YES UAF NETWORK KPANIC DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=7 ActionableScoreLower=5 ## 1. ActionableScore * Conservative score: **5** * Paranoid score: **7** * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * **Local unprivileged trigger: +1**. A local process with access to RDMA uverbs or equivalent bnxt_re device permissions can plausibly create and destroy SRQs. * **Firmware-mediated external influence: +1**. The corrupting write is tied to an NQ interrupt arriving during firmware teardown. * **Memory corruption, weak or indirect corruption candidate: +1**. The patch describes a write into an already freed page, but the written toggle values and reuse target are not shown to be attacker-controlled. * **Real lifetime corruption: +1**. This is a genuine lifetime ordering bug where `free_page()` happens before the firmware teardown path can no longer access the page. * **Reliable kernel crash / strong DoS: +1**. A write-after-free into reclaimed kernel memory can realistically crash or destabilize the kernel. * **Weak LPE concern: +1**. Writable use-after-free on a freed kernel page can become security-relevant if the page is reallocated for another kernel object, but no concrete reclaim primitive is demonstrated. * **Hard or unreliable race / special timing required: -1**. The issue depends on an NQ interrupt racing with `bnxt_qplib_destroy_srq()`. Paranoid adjustment: * **Memory corruption upgraded from weak +1 to strong +2**. In the paranoid view, the explicit write-after-free into a freed page is treated as a strong corruption primitive even though payload and target control are not demonstrated. * **Privileged kernel/device-management memory corruption path: +1**. The corruption occurs in a trusted RDMA driver teardown path involving firmware/device interrupt activity. ## 3. Reachability analysis The bug is locally triggerable by a process that can use the affected bnxt_re RDMA device and create/destroy SRQ objects. This is normally not a fully remote network attack, because a remote RDMA peer does not directly destroy the local SRQ object. However, device and firmware interrupt timing can influence the vulnerable window. Namespaces and containers matter only if RDMA uverbs access is delegated into the container or to a reduced-privilege service account. In typical hardened deployments, access to RDMA devices is restricted, but it is not equivalent to full host root when granted to workloads. The path is hardware and driver dependent, requiring Broadcom bnxt_re RDMA support and the SRQ toggle page feature. Call-site confidence: **high**, because the patch directly shows the ordering of `hash_del()`, `bnxt_qplib_destroy_srq()`, and `free_page()`, and the commit explicitly states that an interrupt can write to the already freed page. ## 4. Severity interpretation This is not an ordinary Moderate resource leak or validation-only fix. It is a real lifetime bug with an explicit write-after-free condition in a kernel RDMA driver. Realistic exploitation evidence points first to local kernel crash or device/kernel state corruption, while privilege escalation remains theoretical because no attacker-controlled reclaim, payload control, or object replacement primitive is shown. Conservative handling is **Actionable Moderate**. Paranoid handling is a **Strong Important candidate** because writable UAF in a device interrupt/firmware teardown path is historically worth manual review even when exploitation details are not demonstrated. ## 5. One-sentence report phrase A race in the bnxt_re SRQ destroy path can free the SRQ toggle page before firmware teardown completes, allowing an NQ interrupt to write toggle values into freed kernel memory and creating a local write-after-free condition with DoS and possible privilege-escalation concern. ## 6. Manual review recommendation **MANUAL CHECK REQUIRED** Reason: the patch fixes an explicit write-after-free lifetime race, not a simple crash-only NULL dereference or resource leak. The practical LPE path is not proven, but the primitive is strong enough to require manual review. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: RDMA/bnxt_re: Free SRQ toggle page after firmware teardown [ Upstream Commit: 104a7ff382a58a83cae018925e3574c784e8274c Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=104a7ff382a58a83cae018925e3574c784e8274c 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=104a7ff382a58a83cae018925e3574c784e8274c ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72500 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72500 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:L/I:L/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7 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: 5 Paranoid ActionableScore: 7 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).