From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-72469][MODERATE 7.0] xprtrdma: Fix ep kref imbalance on ADDR_CHANGE [ Upstream Date: Sat, 15 Aug 2026 06:54:23 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-72469 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: cfd1bab66b042da7a778786685125656c695931b List-Id: CVE: CVE-2026-72469 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: xprtrdma: Fix ep kref imbalance on ADDR_CHANGE [ Upstream Commit: cfd1bab66b042da7a778786685125656c695931b Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cfd1bab66b042da7a778786685125656c695931b Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72469 Analysis date: Sat, 15 Aug 2026 06:54:23 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum**:: Paranoid handling is justified because this is a real kref/lifetime bug with a plausible UAF in kernel RPC/RDMA transport state, but realistic exploitation evidence still looks closer to Actionable Moderate than confirmed Important. Manual review required: YES Summary: An xprtrdma kref imbalance can occur when RDMA_CM_EVENT_ADDR_CHANGE arrives before RDMA_CM_EVENT_ESTABLISHED, causing an unmatched ep put, kref underflow, and a plausible use-after-free during disconnect, with impact primarily kernel crash DoS and possible higher impact requiring manual review. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72469 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72469 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-2026-72469 MODERATE CHECK WITH IMPACT FROM ORIG NN MODERATE 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-911;*CWE-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'An ep kref imbalance in xprtrdma can occur when RDMA_CM_EVENT_ADDR_CHANGE is delivered before RDMA_CM_EVENT_ESTABLISHED. The handler previously followed the disconnected path and dropped an ep reference that had not been acquired, allowing the kref to underflow during connect teardown and leaving rpcrdma_xprt_disconnect operating on a freed ep. This is a race and reference counting bug with a plausible use after free primitive, so impact is at least denial of service via kernel crash and in the paranoid case may include confidentiality and integrity impact. For the CVSS the PR:L is used for the paranoid score because reliable triggering is expected to require local code or a reduced capability network management context that can drive RPC/RDMA connection teardown or RDMA address change timing. The issue is not Internet reachable in typical deployments and is limited to systems using RPC/RDMA or NFS over RDMA on a local RDMA fabric.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5) YES REMOTE OOB INIT UAF NETWORK KPANIC NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: Paranoid handling is justified because this is a real kref/lifetime bug with a plausible UAF in kernel RPC/RDMA transport state, but realistic exploitation evidence still looks closer to Actionable Moderate than confirmed Important. ## 2. Signal breakdown Conservative signals: * +1 Firmware-mediated external influence: the trigger is an RDMA CM event such as ADDR_CHANGE, not ordinary Internet packet parsing. * +1 Memory corruption, weak/indirect corruption candidate: the patch describes operation on a freed ep object, but no attacker-controlled reclaim or overwrite primitive is shown. * +1 Real lifetime corruption: unmatched rpcrdma_ep_put causes kref underflow and premature ep destruction. * +1 Reliable kernel crash / strong DoS: rpcrdma_xprt_disconnect operating on a freed ep can plausibly crash the kernel. * +1 Privileged kernel/device-management lifetime path: this is RDMA transport connection lifecycle state in a trusted kernel networking/storage path. * +1 Availability impact realistic: failure is host-kernel availability impact, not just a warning. * -1 Hard or unreliable race / special timing required: ADDR_CHANGE must arrive before ESTABLISHED and during a narrow connection lifecycle window. * -1 Rare AND difficult-to-reach subsystem/configuration: requires RPC/RDMA or NFS over RDMA deployment. Paranoid delta: * +1 Local unprivileged trigger concern: on systems with an existing NFS/RDMA mount, ordinary local users or services may be able to generate RPC activity and reconnect pressure, while RDMA address-change timing may be influenced by the fabric or management context. Not awarded: * No +2 remote reachable: this is not Internet-reachable in typical deployments. * No +2 strong LPE plausibility: UAF exists, but the patch does not show controlled reclaim, stale callback dispatch, type confusion, arbitrary write, or object replacement. * No confidentiality/integrity impact in the conservative score: no concrete disclosure or write primitive is demonstrated. Call-site confidence: high. The commit message gives the reference-count lifecycle and the affected handler path directly. ## 3. Reachability analysis The affected path is reachable only on systems using RPC/RDMA, commonly NFS over RDMA, and depends on RDMA CM connection events. Typical Internet attackers cannot trigger it directly. A realistic attacker would need local access to a system using an existing RDMA-backed mount, control over workload that causes connection activity, or influence over the RDMA fabric or device-management conditions that produce ADDR_CHANGE before ESTABLISHED. Namespaces and containers may matter if a reduced-privilege service, container root, or delegated storage workload can exercise the mounted RPC/RDMA transport. However, creating and configuring NFS/RDMA mounts and RDMA devices is normally privileged. ## 4. Severity interpretation This is not an ordinary low-risk cleanup because the patch fixes a real kref imbalance leading to premature free and later use of the same ep pointer. It is also not a confirmed Important/LPE issue because there is no demonstrated reclaim, overwrite, callback control, type confusion, or arbitrary memory access. Realistic severity is borderline to actionable Moderate. Paranoid triage should not auto-close it because lifetime corruption in kernel RDMA transport state can be underestimated and deserves manual review. ## 5. One-sentence report phrase An xprtrdma kref imbalance can occur when RDMA_CM_EVENT_ADDR_CHANGE arrives before RDMA_CM_EVENT_ESTABLISHED, causing an unmatched ep put, kref underflow, and a plausible use-after-free during disconnect, with impact primarily kernel crash DoS and possible higher impact requiring manual review. ## 6. Manual review recommendation MANUAL CHECK REQUIRED. Reason: real lifetime corruption and plausible UAF are explicitly described, but exploitation beyond DoS is not proven and depends on RDMA-specific timing and deployment conditions. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: xprtrdma: Fix ep kref imbalance on ADDR_CHANGE [ Upstream Commit: cfd1bab66b042da7a778786685125656c695931b Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cfd1bab66b042da7a778786685125656c695931b Changed files: net/sunrpc/xprtrdma/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=cfd1bab66b042da7a778786685125656c695931b ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72469 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72469 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:H/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: 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).