From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-92486][LOW] bpf: Fix CFI mismatch in task work callback [ Upstream Date: Fri, 18 Sep 2026 00:06:17 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-92486 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: 85a33c910edc3651f68b17ae3c597c012545958f List-Id: CVE: CVE-2026-92486 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: bpf: Fix CFI mismatch in task work callback [ Upstream Commit: 85a33c910edc3651f68b17ae3c597c012545958f Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=85a33c910edc3651f68b17ae3c597c012545958f Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-92486 Analysis date: Fri, 18 Sep 2026 00:06:17 -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-2026-92486 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-92486 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-2026-92486 LOW https://www.kernelcve.org/list/?q=CVE-2026-92486 CHECK WITH IMPACT FROM ORIG NN LOW 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-843;CWE-704;CWE-703;BEST CVSS score: '5.5';DESCR 'A BPF task work callback can be invoked through an incompatible three argument function pointer even though BPF subprograms use the five argument bpf_callback_t ABI. On kernels with kCFI enabled the indirect call can fail CFI validation and may terminate the kernel when the callback executes. For the CVSS the PR:L because triggering requires a local process with permission to load and use the affected BPF task work functionality, typically CAP_BPF or comparable delegated BPF privileges. The issue is not network reachable and impact is denial of service only. There is no evidence in the patch of use after free, out of bounds access, arbitrary memory modification, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) SKIP CVE-2026-92486 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE WARNONLY BPF SIMPLEFIX LINUS INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - 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**:: The conservative and paranoid scores are identical because the supplied patch establishes a kCFI-detected ABI mismatch and DoS behavior only. It does not establish a memory corruption, lifetime, authorization, disclosure, or privilege-escalation primitive. 2. Signal breakdown * +1 Reliable kernel crash / strong DoS: A BPF task-work callback is invoked through an incompatible function pointer type. On kernels with kCFI enabled, the indirect call fails CFI validation when the callback executes and can terminate the kernel. No additional points awarded: * No UAF or stale-object lifetime violation is established. * No controlled reclaim, object replacement, refcount corruption, arbitrary write, OOB access, callback hijack, or type-confusion execution primitive is established. * No confidentiality or integrity impact is established. * No remote reachability is established. * No local-unprivileged-trigger point is awarded because the complete BPF load, verifier acceptance, task-work-kfunc availability, and execution chain is not demonstrated as available to ordinary unprivileged users. * No privilege penalty is applied because host-admin-equivalent privilege is not positively established. The evidence indicates a BPF privilege-gated path, but does not resolve the complete relevant privilege boundary. * No separate availability point is awarded because the kernel failure is already counted as the single strong DoS signal. * No paranoid escalation is awarded. A function-pointer ABI mismatch blocked by kCFI is not evidence of attacker-controlled indirect-call execution. 3. Reachability analysis The triggering actor is a local BPF user that can load and execute a BPF program using the affected task-work scheduling functionality. The exact complete permission chain is not visible in the supplied patch. BPF program loading is normally privilege-gated through CAP_BPF, CAP_SYS_ADMIN, or product-specific delegated BPF permissions. However, the supplied material does not establish whether all required stages, including program loading, verifier approval, use of the task-work kfunc, and callback execution, are available below host-admin-equivalent privilege in the evaluated deployment. The issue is not network reachable. No netdevice attachment, XDP setup, namespace-local trigger, or hardware prerequisite is shown. kCFI must be enabled for the described failure mode to occur. Namespace-scoped reachability is unresolved because the patch does not show that the complete BPF task-work path can be exercised solely with attacker-obtainable namespace-scoped privileges. 4. Primitive and severity interpretation The exact primitive is an incompatible indirect-call function-pointer type. BPF subprogram callbacks follow the five-argument bpf_callback_t ABI, while the vulnerable task-work path stores and invokes the callback through a three-argument function-pointer type. This is an invalid-state and CFI-validation failure, not a UAF, double free, OOB access, ownership violation, or active-object lifetime bug. The vulnerable call is blocked by kCFI rather than causing a demonstrated attacker-controlled reinterpretation of callback data or control flow. PrimitiveClass is CLASS_C because the demonstrated outcome is a kernel fault or DoS from invalid ABI usage. There is no patch-supported evidence of leverage beyond the crash. ImportantCandidate is NO because no meaningful unresolved corruption or security-boundary primitive remains after excluding the DoS consequence. AutoDowngradeAllowed is YES because the issue is constrained to a CFI-detected crash path and does not contain a concrete corruption primitive needing further exploitation review. Likely operational severity is low to ordinary Moderate. Systems without kCFI are not affected by the described CFI mismatch failure mode. 5. One-sentence report phrase A BPF task-work callback ABI mismatch can trigger a kCFI failure and kernel DoS when an affected privileged BPF callback executes, with no demonstrated memory-corruption or privilege-escalation primitive. 6. Manual review recommendation NO MANUAL CHECK NEEDED The patch establishes a deterministic CFI type mismatch and crash-only behavior without a UAF, arbitrary memory access, authorization bypass, or other unresolved kernel-corruption primitive. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: bpf: Fix CFI mismatch in task work callback [ Upstream Commit: 85a33c910edc3651f68b17ae3c597c012545958f Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=85a33c910edc3651f68b17ae3c597c012545958f Changed files: kernel/bpf/helpers.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=85a33c910edc3651f68b17ae3c597c012545958f ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-92486 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-92486 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: 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).