From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-89505][MODERATE REGULAR] RDMA/uverbs: Guard legacy bundles without method_elm Date: Sat, 12 Sep 2026 03:39:10 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-89505 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 3 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: edae84e5461749ed9adf9fcf5c6e075381040ac3 List-Id: CVE: CVE-2026-89505 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: RDMA/uverbs: Guard legacy bundles without method_elm Commit: edae84e5461749ed9adf9fcf5c6e075381040ac3 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=edae84e5461749ed9adf9fcf5c6e075381040ac3 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89505 Analysis date: Sat, 12 Sep 2026 03:39:10 -0400 ActionableScore: 3 ActionableScore lower bound: unknown Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: A local RDMA uverbs user can trigger an uninitialized method_elm pointer dereference through malformed legacy write input, causing a kernel crash, but no UAF, arbitrary write, information disclosure, or privilege escalation primitive is established. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89505 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89505 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 REGULAR 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-2026-89505 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-89505 CHECK WITH IMPACT FROM ORIG NN IMPORTANT Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H';CWE-824;*CWE-457;**CWE-476;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.1';DESCR 'A wild pointer dereference in RDMA uverbs can occur because the legacy write path builds a uverbs_attr_bundle without a valid ioctl method element and leaves method_elm uninitialized. If malformed provider input makes the common uverbs validation code emit an error message, uverbs_get_handler_fn can dereference this uninitialized pointer and crash the kernel. For the CVSS the PR:L value is used because a local user or process needs access to the RDMA uverbs device node such as /dev/infiniband/uverbs. The issue is not network reachable by itself and is triggered through a local character device interface rather than remote packet traffic. Impact is at least local denial of service via kernel crash. For the paranoid score, limited confidentiality impact is kept as a review sensitive interpretation because the bug reads through an uninitialized kernel pointer, but there is no clear arbitrary write primitive in the provided patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) SKIP CVE-2026-89505 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE WRITE OOB SIMPLEFIX NETWORK LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES ## 1. ActionableScore * Raw conservative score: 3 * Conservative score: 3. No floor or cap applied. * Raw paranoid score: 3 * Paranoid score: 3. No additional paranoid point is awarded because no controlled reclaim, disclosure path, arbitrary write, callback control, or lifetime mutation is established. * Final recommended bucket: **Borderline / manual review recommended**:: ## 2. Signal breakdown Positive signals: * +1 Local below-host-admin trigger. A local process with access to `/dev/infiniband/uverbs*` can submit malformed legacy uverbs write input. * +1 Weak / indirect invalid pointer primitive. `bundle.method_elm` is uninitialized in the legacy write path, and `uverbs_get_handler_fn()` can dereference it. * +1 Reliable kernel crash / strong DoS. A wild or invalid `method_elm` dereference can fault in kernel context. Non-awarded signals: * Real UAF not awarded. The patch shows an uninitialized pointer dereference, not post-free object use. * Concrete repeated release/refcount not awarded. There is no first put/free followed by a second lifetime mutation on the same dangling reference. * Controlled reclaim not demonstrated. * Arbitrary or directed kernel write not demonstrated. * Callback/function-pointer control not demonstrated. The visible issue is dereferencing `method_elm` to read `handler`, not a demonstrated attacker-controlled indirect call. * Confidentiality not awarded. No user-visible disclosure path is established. * Integrity not awarded. No unauthorized modification primitive is established. * Remote reachability not awarded. This is a local uverbs character device path, not packet-triggered RDMA network traffic. * Extra Availability not awarded because the same kernel fault is already counted once. ## 3. Reachability analysis The evaluated attacker is a local user or local process that can open the RDMA uverbs device node and issue legacy write commands. This is below host-admin if device permissions grant uverbs access, which is normal for user verbs deployments, so `HostAdminRequired=NO`. The complete trigger is not shown to be namespace-scoped. It depends on access to the RDMA uverbs character device rather than CAP_NET_ADMIN inside a network namespace, so `NamespaceScopedPrivilege=NO`. No direct network trigger is established. Remote RDMA traffic alone is not shown to reach this path. The vulnerable operation is a local userspace ABI path through `ib_uverbs_write()`. A prior loaded RDMA provider/device is required, but the evidence does not justify a rare-hardware penalty. No race or narrow timing requirement is involved. ## 4. Primitive and severity interpretation The exact primitive is an uninitialized kernel pointer dereference. The legacy write path creates a `uverbs_attr_bundle` without an ioctl method element, and malformed provider input can cause common validation/error handling code to call `uverbs_get_handler_fn()`, which dereferences `bundle->method_elm`. This is not an active-object UAF and not fixed stale storage. It is also not a cleanup/destructor lifetime issue. There is no concrete repeated release/refcount operation. Primitive class is `CLASS_C`: demonstrated behavior is primarily invalid pointer dereference and kernel crash. The demonstrated consequence is local denial of service. A stronger consequence such as LPE is speculative and not supported by the supplied patch. `ImportantCandidate=NO` because no independently useful corruption primitive is established beyond the crash path. `AutoDowngradeAllowed=YES` because the issue is a constrained local crash primitive with no UAF, no repeated lifetime mutation, no authorization bypass, no controlled corruption, and no demonstrated C/I impact. Likely operational severity is borderline Moderate: worth manual review because it is local user reachable kernel memory-safety behavior, but not enough for Important-class triage without additional exploit evidence. ## 5. One-sentence report phrase A local RDMA uverbs user can trigger an uninitialized method_elm pointer dereference through malformed legacy write input, causing a kernel crash, but no UAF, arbitrary write, information disclosure, or privilege escalation primitive is established. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: local user reachable wild pointer dereference in kernel RDMA code should be reviewed, but current evidence supports crash-only impact and does not establish Important-grade exploitation leverage. ## 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: RDMA/uverbs: Guard legacy bundles without method_elm Commit: edae84e5461749ed9adf9fcf5c6e075381040ac3 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=edae84e5461749ed9adf9fcf5c6e075381040ac3 Commit description: The legacy write() path dispatches through a uverbs_api_write_method, but the uverbs_attr_bundle passed to provider code does not have an ioctl method element. If malformed provider input causes the common uverbs validation code to emit an error message, uverbs_get_handler_fn() dereferences the uninitialized method_elm pointer. Initialize method_elm explicitly for legacy bundles and make uverbs_get_handler_fn() return NULL when no ioctl method is present. The legacy dispatcher continues to use its local write method, while the ioctl path continues to use the registered ioctl handler. Cc: stable@vger.kernel.org Fixes: 7122ff9 ("RDMA/core: Do not read wild stack memory in uverbs_get_handler_fn()") Link: https://patch.msgid.link/r/AOYAQgCQK3IXqJLr1TB5Qao9.1.1787036796115.Hmail.242270054@hdu.edu.cn Signed-off-by: Yuhang Pan <242270054@hdu.edu.cn> Signed-off-by: Jason Gunthorpe Signed-off-by: Greg Kroah-Hartman Changed files: drivers/infiniband/core/ib_core_uverbs.c drivers/infiniband/core/uverbs_main.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=edae84e5461749ed9adf9fcf5c6e075381040ac3 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-89505 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89505 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:N/A:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/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: unknown Paranoid ActionableScore: 3 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: NO Published priority for this report (same as in Subject): MODERATE REGULAR 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).