From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98007][LOW] bpf: Reject non-scalar bpf_loop iteration counts [ Upstream Date: Sat, 26 Sep 2026 16:33:07 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98007 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 1 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 656d40d1ca228ee21a9b3280432479fc9eae75ab List-Id: CVE: CVE-2026-98007 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: bpf: Reject non-scalar bpf_loop iteration counts [ Upstream Commit: 656d40d1ca228ee21a9b3280432479fc9eae75ab Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=656d40d1ca228ee21a9b3280432479fc9eae75ab Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98007 Analysis date: Sat, 26 Sep 2026 16:33:07 -0400 ActionableScore: 1 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98007 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98007 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: LOW 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-2026-98007 LOW https://www.kernelcve.org/list/?q=CVE-2026-98007 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-20;CWE-617;CWE-754;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'A privileged BPF program can pass a pointer value as the bpf_loop iteration count because the helper previously accepted ARG_ANYTHING. The verifier then marks the register precise and attempts scalar precision backtracking, which triggers a backtracking misuse warning. Systems with panic_on_warn enabled can panic and suffer a local denial of service. For the CVSS the paranoid PR:L reflects environments where a delegated BPF capable service account or container root can load the required program without being a full system administrator. The attack is local and requires the panic_on_warn configuration. No confidentiality or integrity impact is supported because the patch indicates a verifier warning path and does not show a memory corruption primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) YES WARNONLY BPF SIMPLEFIX LINUS SYZBOT YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 1 * Conservative score: 1 * Raw paranoid score: 1 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate**:: No floor or cap was applied. 2. Signal breakdown * +1 Reliable kernel crash / strong DoS. A privileged BPF program can trigger the verifier backtracking misuse warning through a pointer supplied as bpf_loop nr_loops. When panic_on_warn is enabled, the warning causes a kernel panic. Important non-awarded signals: * No memory corruption bonus. The patch establishes invalid helper argument validation and a WARN path, not UAF, OOB access, type confusion, arbitrary write, or stale-object use. * No confidentiality or integrity points. There is no read-back, disclosure, unauthorized modification, or security-boundary bypass. * No local unprivileged trigger point. The supplied evidence explicitly identifies privileged BPF programs, while the complete evaluated privilege model is not established. * No delegated privilege penalty. Delegated CAP_BPF or container reachability is possible in some deployments but is not established for the complete trigger chain. * No host-admin penalty. Host-admin-equivalent privilege is not positively established by the supplied evidence. * No remote reachability point. The vulnerable path is local BPF verifier processing. * No extra availability point. The panic is the same consequence already counted by the single DoS point. * No paranoia-only point. The patch-supported behavior remains a warning-to-panic path and does not establish a stronger corruption primitive. 3. Reachability analysis The attacker must load a BPF program that invokes bpf_loop with a pointer-valued first argument. The commit explicitly describes this as a privileged-program path. The complete privilege requirement depends on the evaluated kernel and product policy, including CAP_BPF, CAP_SYS_ADMIN, unprivileged BPF settings, LSM policy, and any delegated BPF access. HostAdminRequired is UNKNOWN because the supplied patch proves that privileged BPF is required but does not establish whether the relevant capability is host-admin-equivalent or delegated to a lower-privilege service or container actor. NamespaceScopedPrivilege is also UNKNOWN because no evidence establishes that program loading and the complete trigger path are available inside an attacker-controlled namespace. The fatal consequence additionally requires panic_on_warn to be enabled. This is an externally configured condition and is not normally assumed to be enabled by default. No special hardware, network service, device, or race is involved. 4. Primitive and severity interpretation The exact primitive is an invalid verifier-helper argument type reaching precision backtracking. bpf_loop accepted ARG_ANYTHING for an iteration count that must be scalar, allowing a pointer register to reach code that assumes a scalar precise register. This causes a backtracking misuse WARN. This is not a UAF, refcount bug, ownership violation, stale-pointer path, or active-object lifetime issue. It is CLASS_C because the demonstrated security-relevant behavior is invalid-state handling that can become a local kernel DoS when panic_on_warn is enabled. The patch does not establish attacker-controlled memory corruption, controlled reclaim, arbitrary read or write, callback influence, privilege escalation, or a security-boundary bypass. Therefore ImportantCandidate is NO and AutoDowngradeAllowed is YES. Operationally, this is a configuration-dependent local DoS affecting systems that both permit the relevant privileged BPF operation and enable panic_on_warn. 5. One-sentence report phrase A privileged BPF program can pass a non-scalar bpf_loop iteration count and trigger a verifier warning which causes a local kernel panic when panic_on_warn is enabled. 6. Manual review recommendation NO MANUAL CHECK NEEDED The patch establishes a validation-only verifier bug with a configuration-dependent panic outcome and no concrete memory-corruption, lifetime, authorization, disclosure, or privilege-escalation primitive. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: bpf: Reject non-scalar bpf_loop iteration counts [ Upstream Commit: 656d40d1ca228ee21a9b3280432479fc9eae75ab Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=656d40d1ca228ee21a9b3280432479fc9eae75ab Changed files: include/linux/bpf.h kernel/bpf/bpf_iter.c kernel/bpf/verifier.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=656d40d1ca228ee21a9b3280432479fc9eae75ab ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98007 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98007 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:H/PR:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.7 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: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW 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).