From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-99166][MODERATE 7.0] net: rds: fix uninitialized trans dereference in CM event handler Date: Thu, 29 Oct 2026 00:21:42 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-99166 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: 3 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 5f23e4e3a31dacfd82a8f56be253adc0910ee84f List-Id: CVE: CVE-2026-99166 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: net: rds: fix uninitialized trans dereference in CM event handler Commit: 5f23e4e3a31dacfd82a8f56be253adc0910ee84f Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5f23e4e3a31dacfd82a8f56be253adc0910ee84f Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99166 Analysis date: Thu, 29 Oct 2026 00:21:42 -0400 ActionableScore: 3 ActionableScore lower bound: unknown Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: An adjacent RDMA peer can crash a suitably configured RDS host by driving non-IB CM events into an uninitialized transport call or unset route record. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99166 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99166 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-2026-99166 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99166 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=4 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H';*CWE-457;CWE-824;**CWE-476;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.6';DESCR 'RDS RDMA CM handling can use an uninitialized transport pointer when an event arrives on a non-IB RDMA device. A remote peer with access to the adjacent RDMA fabric can send a connect request to an RDS listener on an iWARP device and trigger an invalid indirect call that normally causes a kernel oops. The active path can also bind to a non-IB device and later access an unset route path record. For the CVSS the PR:N value is selected because the listener side requires no authenticated session or local user context beyond reachability to the exposed RDS RDMA endpoint. Availability impact is confirmed. Limited confidentiality or integrity impact is retained only in the paranoid score because an uninitialized pointer reaches an indirect call and another path performs an invalid memory write, but attacker control sufficient for privilege escalation is not established. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 7.6 and the production ActionableScore returned 3 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the manual review requirement was applied. ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore threshold rule was applied. final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 6.5 and ActionableScore 4 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) MAYBE OOB NULLPTR INIT LEAK KERNEL_PANIC_PLUS_UAF HARDWARE INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 3 (+2 network reachability, +1 crash, +1 invalid indirect-pointer consumption, -1 unusual RDS/iWARP configuration). * Conservative score: 3; no floor or cap applied. * Raw paranoid score: 3; unsupported confidentiality, integrity, or control-flow exploitation was not added. * Paranoid score: 3. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown * +2 — An unauthenticated peer with access to the adjacent RDMA fabric can send a connection request to an exposed RDS listener. * +1 — The uninitialized `trans` is dereferenced for an indirect function call; Clang/zero-initialized builds plausibly produce a kernel oops. * +1 — Weak indirect-corruption concern: an uninitialized pointer is consumed as a transport object, but attacker influence over its value is not shown. * -1 — The vulnerable listener requires the unusual combination of RDS and a non-IB RDMA device; the commit states that iWARP transport support was removed long ago. * The active path’s unset `path_rec[0].sl` write is another crash-capable invalid access, not a confirmed heap OOB or attacker-directed target; it is not separately stacked. * No controlled call target, arbitrary write, disclosure, UAF, retry-accumulated OOB, or authorization bypass is shown. The same crash receives no additional availability point. 3. Reachability analysis The listener-side trigger is remote/adjacent and requires neither host UID 0 nor host-administrator capability from the attacking peer. It presupposes that the victim exposes an RDS listener on an iWARP/siw device, but the supplied evidence does not establish a separate attacker-controlled privileged setup. No namespace capability or race is involved. 4. Primitive and severity reading The patch shows consumption of an uninitialized transport pointer and, on the active path, access through an unset route record. Both primarily support host crash/DoS. The pointer reaches an indirect call, but its value is compiler/stack-derived rather than attacker-controlled; the route write likewise lacks a controlled valid target. This is therefore CLASS_C, not a useful memory-corruption or control-flow primitive. Important-grade confidentiality, integrity, or code execution remains theoretical and unsupported, so automatic Important preservation is unwarranted. 5. One-sentence report phrase An adjacent RDMA peer can crash a suitably configured RDS host by driving non-IB CM events into an uninitialized transport call or unset route record. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm product exposure to RDS over iWARP/siw and affected compiler initialization behavior. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net: rds: fix uninitialized trans dereference in CM event handler Commit: 5f23e4e3a31dacfd82a8f56be253adc0910ee84f Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5f23e4e3a31dacfd82a8f56be253adc0910ee84f Commit description: rds_rdma_cm_event_handler_cmn() assigns trans only when the RDMA device is an InfiniBand CA (RDMA_NODE_IB_CA). On any other device type, e.g. an iWARP RNIC such as siw, trans stays uninitialized, but the event switch dereferences it: unconditionally in the RDMA_CM_EVENT_CONNECT_REQUEST case via trans->cm_handle_connect(), and (with a connection context) in the ROUTE_RESOLVED and ESTABLISHED cases. An RDS listener on an iWARP device therefore crashes the kernel as soon as a connect request arrives: with CONFIG_INIT_STACK_ALL_ZERO the wild load becomes a NULL dereference at offset 0xa0 (&trans->cm_handle_connect) in the iw_cm_wq workqueue. GCC masks the bug in default builds by folding the uninitialized load into &rds_ib_transport; Clang-built kernels take the real uninitialized path and oops. The active side can land on a non-IB device too: the id that rds_ib_conn_path_connect() creates is not restricted to a node type, so rdma_resolve_addr() binds it to whichever device serves the local address, and an iWARP RNIC on the same netdev qualifies. The crash there is different: resolving a route on an iWARP id never fills in cm_id->route.path_rec, and the ROUTE_RESOLVED case writes path_rec[0].sl before it calls into the transport. The iWARP transport was dropped long ago and IB is the only transport left, so make that explicit: initialize trans to &rds_ib_transport at declaration, drop the conditional assignment, reject a connect request that arrives on a non-IB device, and drop a connection whose address resolved to one instead of resolving a route on it. The rejection is limited to RDMA_CM_EVENT_CONNECT_REQUEST on purpose: a non-zero return from the handler makes rdma_cm destroy the id the event was delivered on, which is right for the request's freshly created id but would free a connection id that RDS still owns for any other event. On the active side the id stays ic->i_cm_id and the connection's shutdown destroys it, so that case returns 0. Fixes: dcdede0 ("RDS: Drop stale iWARP RDMA transport") Reported-by: TencentOS Corvus AI Link: https://lore.kernel.org/netdev/20260824111701.2979194-1-ljp1205831794@gmail.com/ Link: https://lore.kernel.org/netdev/20260825021223.3483044-1-ljp1205831794@gmail.com/ Cc: stable@vger.kernel.org Assisted-by: CodeBuddy:Kimi-K3 Signed-off-by: Aohan Mei [achender: reject only on RDMA_CM_EVENT_CONNECT_REQUEST instead of bailing out for every event on a non-IB device, so that rdma_cm does not destroy connection ids RDS still tracks; drop a connection whose address resolved to a non-IB device before a route is resolved on it; changelog adjusted] Assisted-by: LLM Signed-off-by: Allison Henderson Link: https://patch.msgid.link/20261003163408.250568-2-achender@kernel.org Signed-off-by: Paolo Abeni Signed-off-by: Greg Kroah-Hartman Changed files: net/rds/rdma_transport.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=5f23e4e3a31dacfd82a8f56be253adc0910ee84f ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99166 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99166 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:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 7.6 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: 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).