From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-89528][MODERATE 7.0] svcrdma: Reject Read lists that exceed the page budget [ Upstream Date: Sat, 12 Sep 2026 06:19:54 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-89528 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: unknown X-AL-KERNEL-Commit: 1a3af2262cb384112ef38632de4690682be528b4 List-Id: CVE: CVE-2026-89528 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: svcrdma: Reject Read lists that exceed the page budget [ Upstream Commit: 1a3af2262cb384112ef38632de4690682be528b4 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1a3af2262cb384112ef38632de4690682be528b4 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89528 Analysis date: Sat, 12 Sep 2026 06:19:54 -0400 ActionableScore: 4 ActionableScore lower bound: unknown Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89528 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89528 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-2026-89528 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-89528 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';*CWE-20;**CWE-476;CWE-770;BEST CVSS score: '6.5';DESCR 'An RPC/RDMA Read list handling flaw in svcrdma can cause a NULL-pointer dereference because each Read segment length is checked individually but the cumulative length across all segments is not bounded by the receive page budget. A remote RDMA peer can send multiple Read segments whose total size exceeds the rq_pages array budget. When one segment exactly consumes the page array, the following segment reaches the rq_pages sentinel slot and the server later dereferences a NULL page pointer during DMA mapping, causing a kernel crash (DoS). For the CVSS the PR:N is selected because a peer only needs network reachability to the NFS/RDMA service and no local account on the victim is required. The issue is network reachable only on systems that expose the RPC/RDMA or NFS/RDMA service, typically on storage or data center RDMA networks rather than the public Internet. Impact is denial of service via kernel crash, with no grounded evidence of information disclosure or privilege escalation from this patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) YES REMOTE NULLPTR SIMPLEFIX NETWORK DMAorINTERRUPT KPANIC NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=REQUIRED AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 4 * Conservative score: 4 * Raw paranoid score: 4 * Paranoid score: 4 * No floor or cap changed the score. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown Positive signals: * +2 Remote reachable / directly network-triggerable: an RPC/RDMA or NFS/RDMA requester can send a malformed Read list to an exposed svcrdma service. * +1 Reliable kernel crash / strong DoS: the commit explicitly states that the overflowed Read list can reach the NULL sentinel at rq_pages[rq_maxpages] and cause a NULL pointer dereference during DMA mapping. * +1 Memory layout / length-budget invariant restoration: the patch restores consistency between cumulative Read segment lengths and the rq_pages array budget by checking PAGE_ALIGN(total_len) against maxlen. Negative signals: * 0 No host-admin penalty: the attacker does not need local host administration once the RPC/RDMA service is reachable. * 0 No race penalty: this is an ordered malformed input validation failure, not a timing race. * 0 No rare-subsystem penalty: NFS/RDMA is specialized and often internal, but the prompt requires concrete evidence before subtracting for deployment rarity. Important non-awarded signals: * Controlled reclaim not demonstrated. * Arbitrary write not demonstrated. * Real UAF not established. * Concrete repeated release/refcount operation not established. * Confidentiality and integrity impact not awarded because the established primitive is a NULL pointer dereference crash. * Extra Availability not awarded because the same kernel crash is already counted once. * Strong LPE or privilege escalation not awarded. * ImportantCandidate is not set because this is a crash-only Class C primitive without unresolved memory-corruption leverage. 3. Reachability analysis The evaluated attacker is a remote RPC/RDMA peer that can reach the NFS/RDMA service. No local account on the victim is required, so HostAdminRequired=NO. The complete trigger requires that the target system has svcrdma / NFS over RDMA enabled and reachable. This is prior service exposure, not attacker privilege on the victim. In practice these services are usually deployed on storage or data-center RDMA networks rather than the public Internet, but that limits exposure rather than changing the primitive. Namespace-scoped privilege is not relevant to the complete trigger, so NamespaceScopedPrivilege=NO. No sysctl, boot option, or local capability requirement for the attacker is shown. RDMA-capable infrastructure is required for exposure, but this is not enough to apply a physical-only or rare-hardware penalty under the provided rules. The trigger is not a race and should be repeatable with malformed protocol input. 4. Primitive and severity interpretation The exact primitive is missing cumulative bounds validation for RPC/RDMA Read segments. Individual segment lengths were checked, but the sum of multiple segments could exceed the receive page budget. When the page array is exactly consumed, the next segment can cause access to the NULL sentinel slot and later dereference a NULL page pointer during DMA mapping. This is not an active structured UAF and not fixed stale storage. It is a malformed input / invalid state / NULL dereference path. There is no concrete repeated release/refcount operation. The first lifetime operation, second lifetime mutation, and dangling reference requirements do not apply. PrimitiveClass=CLASS_C because the demonstrated behavior is kernel crash / DoS without an independently useful corruption primitive. The demonstrated consequence is host kernel DoS. The speculative consequence would be stronger corruption or privilege escalation, but the patch and supplied context do not support such a mechanism. ImportantCandidate=NO because there is no Class A primitive and no strong Class B unresolved lifetime/corruption primitive. AutoDowngradeAllowed=YES because this can be treated as non-Important after exposure review, although it should not be ignored on systems exposing NFS/RDMA. Likely operational severity is an actionable network-adjacent DoS for exposed RPC/RDMA servers, especially inside storage networks. 5. One-sentence report phrase A malformed RPC/RDMA Read list can exceed the svcrdma receive page budget and trigger a NULL pointer dereference during DMA mapping, allowing a reachable RDMA peer to crash the kernel. 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the issue is network reachable on systems exposing RPC/RDMA or NFS/RDMA and can cause a kernel crash, even though no UAF, arbitrary write, information disclosure, or privilege escalation primitive is established. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: svcrdma: Reject Read lists that exceed the page budget [ Upstream Commit: 1a3af2262cb384112ef38632de4690682be528b4 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1a3af2262cb384112ef38632de4690682be528b4 Changed files: net/sunrpc/xprtrdma/svc_rdma_recvfrom.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=1a3af2262cb384112ef38632de4690682be528b4 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89528 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89528 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: Not available The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 6.5 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: 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).