From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98613][MODERATE REGULAR] bpf: Bound ownership depth through local kptrs and graph roots [ Upstream Date: Sat, 24 Oct 2026 12:38:49 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98613 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: 1 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 92aa0502c781d72bb9685245c3280efb3766a110 List-Id: CVE: CVE-2026-98613 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: bpf: Bound ownership depth through local kptrs and graph roots [ Upstream Commit: 92aa0502c781d72bb9685245c3280efb3766a110 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=92aa0502c781d72bb9685245c3280efb3766a110 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98613 Analysis date: Sat, 24 Oct 2026 12:38:49 -0400 ActionableScore: 1 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: Crafted BPF local-object ownership chains can recursively exhaust the kernel stack when their head object is dropped, causing a host kernel crash. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98613 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98613 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-2026-98613 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98613 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE AEGIS_AS=1 LEGACY=MODERATE RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE) 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:N/A:H';CWE-674;**CWE-400;CWE-770;BEST CVSS score: '5.5';DESCR 'Program allocated BPF objects can form cyclic or deeply nested ownership chains through local referenced kptrs and graph roots. Synchronous destruction follows each ownership edge through bpf_obj_free_fields() and __bpf_obj_drop_impl(), so dropping the head can exhaust the kernel stack and crash the host. For the CVSS the PR:L value reflects the need for a local user or process able to load BTF and BPF programs, allocate the affected objects, and trigger their destruction. The demonstrated primitive is uncontrolled recursion and kernel stack exhaustion rather than UAF, OOB access, or an arbitrary write, so the supported impact is availability loss without proven confidentiality or integrity impact. The issue is not directly network reachable. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 5.5 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. 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. The independent weaker Aegis shadow evaluated CVSS 5.5 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE INIT BPF NOMEMCHK UAF HARDWARE LINUS TEST - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 1. * Conservative score: 1; no floor or cap changed it. * Raw paranoid score: 1. * Paranoid score: 1; stronger impact would require unsupported memory-corruption or reachability assumptions. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 Reliable kernel crash/strong DoS: attacker-defined local BTF ownership chains can make synchronous `bpf_obj_free_fields()` / `__bpf_obj_drop_impl()` recursion exhaust the kernel stack. * +0 Additional availability: withheld because it would duplicate the same stack-exhaustion crash. * No UAF, OOB read/write, arbitrary write, stale object, controlled reclaim, authorization bypass, confidentiality impact, or integrity impact is shown. * No local-unprivileged bonus: the supplied evidence does not establish that the complete BTF load, BPF program load, object allocation, and destruction sequence works for a normal user. * No privilege penalty: effective host-admin privilege is also not positively established. * NEW52/B5-R does not apply: there is no retry-accumulated heap OOB write or later consumption of corrupted heap state. 3. Reachability analysis A local process able to load the relevant BTF/BPF program can define recursive or excessively deep ownership through local referenced kptrs or graph roots, allocate those objects, and trigger destruction. Exact CAP_BPF/CAP_SYS_ADMIN policy and product settings are not supplied, so host-admin and namespace-scoped reachability remain unknown. No remote path, special hardware, prior device setup, or timing race is involved. 4. Primitive and severity reading The primitive is attacker-shaped active ownership topology causing unbounded synchronous recursive destruction and kernel-stack exhaustion. It is neither fixed stale storage nor a lifetime violation: no object is shown used after free, and no repeated release through a dangling reference exists. This is CLASS_C because the demonstrated consequence is host crash/availability loss without a separately useful corruption primitive. ImportantCandidate is NO and auto-downgrade is allowed because the fix adds a depth/cycle validation bound, while the evidence shows no memory corruption or security-boundary breach. 5. One-sentence report phrase Crafted BPF local-object ownership chains can recursively exhaust the kernel stack when their head object is dropped, causing a host kernel crash. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm product-specific BPF loading privileges and whether delegated or namespace-scoped actors can complete the trigger. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: bpf: Bound ownership depth through local kptrs and graph roots [ Upstream Commit: 92aa0502c781d72bb9685245c3280efb3766a110 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=92aa0502c781d72bb9685245c3280efb3766a110 Changed files: kernel/bpf/btf.c tools/testing/selftests/bpf/prog_tests/linked_list.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=92aa0502c781d72bb9685245c3280efb3766a110 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98613 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98613 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:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.5 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: 1 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).