From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98629][MODERATE REGULAR] net/sched: cls_u32: fix manual hash table handle IDR aliasing [ Upstream Date: Sun, 18 Oct 2026 23:07:11 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98629 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: 2 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 21fc07924e996e1e661268ca269c86b8d59d25b3 List-Id: CVE: CVE-2026-98629 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: net/sched: cls_u32: fix manual hash table handle IDR aliasing [ Upstream Commit: 21fc07924e996e1e661268ca269c86b8d59d25b3 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=21fc07924e996e1e661268ca269c86b8d59d25b3 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98629 Analysis date: Sun, 18 Oct 2026 23:07:11 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: An IDR key mismatch in cls_u32 can leak manual hash table entries and alias unrelated live tables, causing incorrect classifier lookup and limited traffic-control disruption for an actor with the required CAP_NET_ADMIN authority. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98629 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98629 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-98629 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98629 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE RESULT=DIFF V39_AEGIS_ONE_STEP_UP=LOW->MODERATE TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L';CWE-682;CWE-706;*CWE-401;*CWE-664;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '4.4';DESCR 'The cls_u32 classifier used different IDR key domains when creating and deleting a hash table with an explicit handle. Handles in the 0x800 to 0xFFF htid range could leave a persistent unreachable IDR entry and could also remove the IDR entry of an unrelated live automatically allocated table. A later allocation could reuse the affected identifier and create two live tables with the same visible handle. The first match behavior in u32_lookup_ht could then direct lookups and TCA_U32_LINK operations to the wrong table, causing incorrect classifier configuration, resource retention, and limited disruption of traffic handling. For the CVSS the PR:L value is used for the paranoid score because a reduced capability container root, service account, or namespace user may be delegated CAP_NET_ADMIN without having unrestricted host administration rights. The issue is not directly network reachable because creating the conflicting tables requires local traffic control configuration through the netlink control plane. The supported impact is limited integrity and availability loss. There is no demonstrated UAF, OOB access, arbitrary write, information disclosure, or host wide resource exhaustion. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 4.4 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE to LOW because the ActionableScore threshold rule was applied. final reconciliation stage LOW to MODERATE because KP specialist did not establish a qualifying panic and 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 DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 and KPANIC_UNSUPPORTED_REMOVED and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 3.4 and ActionableScore 2 with primitive class CLASS_C and manual review RECOMMENDED. 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.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) MAYBE REMOTE LEAK NETWORK LINUS TEST QDISC DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES RequiresHostUID0=NO AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw conservative score: 2 * Conservative score: 2 * Raw paranoid score: 2 * Paranoid score: 2 * No floor or cap was applied. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 Concrete persistent kernel resource leak. A manually keyed table can leave an unreachable IDR entry after deletion. * +1 Weak active-state selection error. Deletion can remove an unrelated IDR entry, after which handle reuse makes `u32_lookup_ht()` and `TCA_U32_LINK` select the wrong live table. * No UAF, OOB access, heap overwrite, repeated release, refcount corruption, or arbitrary write is established. * No reliable kernel crash or host-wide resource exhaustion is demonstrated. * No confidentiality impact is established. * Integrity impact was not separately scored because the affected actor already controls the relevant traffic-control configuration, and no modification of another authority domain is shown. * No remote-trigger bonus. Packets alone cannot create the conflicting IDR state. * No privilege penalty. Host-admin-equivalent privilege is not positively established, but complete attacker-obtainable namespace reachability is also not established. * B5-R, B3-PENDING, V33, V32, and V34 do not apply. There is no memory write primitive or checksum-metadata corruption. * B4-PENDING does not apply. The patch fixes identifier consistency rather than an authorization DENY-to-ALLOW transition. 3. Reachability analysis The trigger uses the `tc` netlink control plane to create and delete `cls_u32` hash tables with selected handles. This requires `CAP_NET_ADMIN` over the affected network context, but the supplied evidence does not establish whether the complete operation is restricted to host administration or available through an attacker-reachable user and network namespace. Host UID 0 is not intrinsically required because Linux capabilities can be delegated independently of UID. No prior physical device, special hardware, boot option, race, or network packet timing is required. The handle sequence is deterministic and repeatable once the required traffic-control authority is available. 4. Primitive and severity interpretation The exact primitive is an IDR key-domain mismatch. Allocation uses the raw manual handle while destruction uses `handle2id(handle)`. This causes a persistent entry leak, removal of an unrelated entry, and later aliasing between live tables. This is active invalid-state consumption because lookup and link operations may select the wrong table. It is not a memory-safety primitive. There is no freed-object use, attacker-directed kernel-memory write, authorization bypass, or demonstrated cross-namespace policy modification. `PrimitiveClass=CLASS_C` reflects deterministic invalid state, limited resource retention, and incorrect object selection. `ImportantCandidate=NO` and `AutoDowngradeAllowed=YES` are appropriate because no unresolved corruption or security-boundary primitive remains. The likely operational severity is Low to ordinary Moderate. 5. One-sentence report phrase An IDR key mismatch in cls_u32 can leak manual hash table entries and alias unrelated live tables, causing incorrect classifier lookup and limited traffic-control disruption for an actor with the required CAP_NET_ADMIN authority. 6. Manual review recommendation NO MANUAL CHECK NEEDED The patch establishes a deterministic bookkeeping and object-selection error, but no memory corruption, authorization bypass, remote trigger, host-wide crash, or unresolved cross-boundary primitive. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net/sched: cls_u32: fix manual hash table handle IDR aliasing [ Upstream Commit: 21fc07924e996e1e661268ca269c86b8d59d25b3 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=21fc07924e996e1e661268ca269c86b8d59d25b3 Changed files: net/sched/cls_u32.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=21fc07924e996e1e661268ca269c86b8d59d25b3 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98629 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98629 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:H/UI:N/S:U/C:N/I:L/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L The Best / paranoid CVSS score: 4.4 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: 2 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).