From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98278][LOW] net: remove WARN_ON_ONCE() from the dev_fill_forward_path() loop check [ Upstream Date: Fri, 09 Oct 2026 05:01:34 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98278 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: 0 X-AL-KERNEL-Commit: d8eb177632dacda28bc6130c2105afbf5b791eb0 List-Id: CVE: CVE-2026-98278 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: net: remove WARN_ON_ONCE() from the dev_fill_forward_path() loop check [ Upstream Commit: d8eb177632dacda28bc6130c2105afbf5b791eb0 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d8eb177632dacda28bc6130c2105afbf5b791eb0 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98278 Analysis date: Fri, 09 Oct 2026 05:01:34 -0400 ActionableScore: 1 ActionableScore lower bound: 0 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-2026-98278 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98278 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-2026-98278 LOW https://www.kernelcve.org/list/?q=CVE-2026-98278 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT LOW AEGIS_AS=0 LEGACY=LOW RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both 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-617;CWE-754;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A reachable WARN_ON_ONCE in dev_fill_forward_path can occur when an IPIP or IPv6 tunnel route resolves back to the same tunnel device and a flowtable operation tries to build an offload path through it. The path walk makes no progress and emits a kernel warning before returning an error. For the CVSS the PR:L value is used because reliable triggering requires CAP_NET_ADMIN to create the routing loop and configure the relevant tunnel and flowtable state, but this capability can be delegated without granting full host administration. The issue is not directly network reachable because receiving network traffic alone does not create the required routing configuration. Normal systems are primarily affected by a warning and failed path construction. Systems configured with panic_on_warn may convert the warning into a kernel panic and host denial of service. No UAF, out of bounds access, information disclosure, arbitrary write, or privilege escalation primitive is supported by the affected code.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE REMOTE OOB SIMPLEFIX HARDWARE LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ActionableScoreLower=0 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 0 * Conservative score: 0 * Raw paranoid score: 1 * Paranoid score: 1 * No floor or cap was applied. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown Conservative signals: * +0 Reachable warning. WARN_ON_ONCE is nonfatal under normal configuration, and the function already returns an error. * +0 Failed path construction. The routing loop is invalid, and failure of this walk is preserved after the patch. * +0 B5-R does not apply. There is no heap OOB write, retry-accumulated index, corrupted descriptor, or later consumption of corrupted state. Paranoid signals: * +1 Reliable kernel crash or strong DoS only on systems configured with panic_on_warn, where the reachable warning may become a kernel panic. Not awarded: * No UAF, OOB access, overwrite, stale object, refcount mutation, disclosure, or authorization bypass. * No direct remote reachability. Network traffic alone cannot create the required tunnel routing loop. * No additional availability point because panic and host failure are the same consequence. * No privilege penalty because CAP_NET_ADMIN is established, but the evidence does not resolve whether the complete trigger requires host-admin-equivalent authority or works entirely with delegated or namespace-scoped authority. * No common networking data-path point because this is a configured flowtable and tunnel control-path condition, not an ordinary packet-only trigger. * No C or I impact and no LPE leverage. 3. Reachability analysis A CAP_NET_ADMIN user must configure an IPIP or IPv6 tunnel whose route resolves back to the same tunnel and cause flowtable offload path construction. This is a local control-plane trigger rather than a remote packet trigger. The supplied evidence does not identify which user namespace governs every required tunnel and flowtable operation. Therefore, complete namespace-scoped reachability and below-host-admin reachability remain unknown. No special hardware, race, narrow timing window, or separate vulnerability is required. 4. Primitive and severity interpretation The exact primitive is a reachable WARN_ON_ONCE followed by the existing error exit. It is neither memory corruption nor a lifetime or ownership violation. No active structured object is used after free, and no repeated release or refcount operation exists. The demonstrated normal consequence is a one-time warning and rejected forward-path walk. The paranoid consequence is host DoS when panic_on_warn converts the warning into a panic. This is CLASS_C rather than CLASS_A or CLASS_B. ImportantCandidate is NO because no corruption or security-boundary primitive exists. AutoDowngradeAllowed is YES because the only security-relevant worst case depends on warning-to-panic policy, with no unresolved exploitation leverage. 5. One-sentence report phrase A CAP_NET_ADMIN controlled tunnel routing loop can reach WARN_ON_ONCE during flowtable path construction and may panic a host configured with panic_on_warn, but it provides no memory corruption or privilege escalation primitive. 6. Manual review recommendation NO MANUAL CHECK NEEDED The B5-R preservation profile is not established, and the patch only removes a reachable diagnostic warning while retaining the same loop detection and error return. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net: remove WARN_ON_ONCE() from the dev_fill_forward_path() loop check [ Upstream Commit: d8eb177632dacda28bc6130c2105afbf5b791eb0 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d8eb177632dacda28bc6130c2105afbf5b791eb0 Changed files: net/core/dev.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=d8eb177632dacda28bc6130c2105afbf5b791eb0 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98278 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98278 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:L/UI:N/S:U/C:N/I:N/A:L 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: 0 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).