From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64355][MODERATE 7.0] bpf: Reject fragmented frames in devmap [ Upstream Date: Sat, 25 Jul 2026 09:13:33 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64355 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 47baddc856ae7e93a565dd9deeb797999b179466 List-Id: CVE: CVE-2026-64355 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: bpf: Reject fragmented frames in devmap [ Upstream Commit: 47baddc856ae7e93a565dd9deeb797999b179466 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=47baddc856ae7e93a565dd9deeb797999b179466 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64355 Analysis date: Sat, 25 Jul 2026 09:13:33 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64355 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64355 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 7.0 Manual review required: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-64355 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';CWE-125;*CWE-787;CWE-908;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'A memory safety issue in the BPF devmap broadcast clone path can occur when fragmented native XDP frames are cloned. The clone copies only the linear xdp_frame data while fragment metadata lives outside the linear area, so the cloned frame can keep XDP_FLAGS_HAS_FRAGS without valid skb_shared_info metadata. During frame return, the free path may interpret uninitialized tail data as fragment metadata and perform an out-of-bounds access. For the CVSS the PR:N because an attacker only needs packet reachability to an already configured XDP devmap broadcast path and does not need local code execution on the victim. The attack is not a generic public Internet service scenario and is more likely in local or data center networks where XDP and devmap redirects are deployed. Impact is at least denial of service via kernel crash. In the paranoid interpretation, the out-of-bounds access in the frame return path is treated as a memory corruption candidate with possible confidentiality and integrity impact, so this should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) YES OOB BPF SIMPLEFIX SKB PACKET KPANIC INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 1. **ActionableScore** * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: 2. **Signal breakdown** * Remote reachable / network-triggerable: +2. A packet can trigger the vulnerable XDP devmap broadcast clone path if the target already has this XDP/devmap configuration active. * Memory corruption, weak/indirect corruption candidate: +1. The clone can preserve `XDP_FLAGS_HAS_FRAGS` without valid `skb_shared_info`, causing bogus metadata interpretation and OOB access during frame return. * Memory layout invariant restoration: +1. The patch restores the invariant between linear frame data and fragment metadata by rejecting fragmented/nonlinear frames before clone. * Reliable kernel crash / strong DoS: +1. The described OOB access during frame return is a credible kernel crash path. * Common packet-processing path: +1. This is in the XDP/network packet-processing datapath, though not in the generic TCP/IP receive path. * Rare AND difficult-to-reach configuration: -1. Requires XDP devmap broadcast redirect and fragmented native XDP or nonlinear generic XDP frames. * Corruption primitive constrained or metadata-only: -1. The patch does not show attacker-controlled overwrite, reclaim, callback control, or arbitrary read/write. * Paranoid-only weak LPE concern: +1. Bogus `skb_shared_info` interpretation in a free/return path may affect page/refcount handling, but no practical privilege-escalation primitive is demonstrated. 3. **Reachability analysis** Triggering does not require loading BPF if the vulnerable XDP/devmap broadcast setup already exists, so packet reachability to that datapath can be enough. Creating or attaching the XDP/BPF/devmap configuration normally requires root, `CAP_BPF`, `CAP_NET_ADMIN`, or equivalent privileges, so no local unprivileged BPF API bonus is awarded. This is not a generic public Internet service scenario. Realistic exposure is more likely in local, L2, data-center, or high-performance networking environments using XDP redirect/broadcast. 4. **Severity interpretation** This is stronger than an ordinary Moderate because the patch describes a concrete memory-safety failure in a packet-processing path, not just validation cleanup. Conservatively, the demonstrated impact is network-adjacent DoS via kernel crash. The paranoid interpretation treats the invalid fragment metadata in the frame return path as a weak corruption candidate, but there is no demonstrated arbitrary write, reclaim primitive, or reliable LPE chain, so this remains Actionable Moderate rather than a strong Important classification. 5. **One-sentence report phrase** A fragmented XDP frame cloned through BPF devmap broadcast can keep frag flags without valid fragment metadata, allowing packet-triggered OOB access during frame return and causing at least a kernel crash in configured XDP deployments. 6. **Manual review recommendation** MANUAL CHECK REQUIRED. The issue is network-triggerable in configured deployments and involves OOB access from invalid fragment metadata in a kernel packet free/return path, so it should not be auto-closed even though the practical LPE evidence is weak. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: bpf: Reject fragmented frames in devmap [ Upstream Commit: 47baddc856ae7e93a565dd9deeb797999b179466 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=47baddc856ae7e93a565dd9deeb797999b179466 Changed files: kernel/bpf/devmap.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=47baddc856ae7e93a565dd9deeb797999b179466 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64355 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64355 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:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7.5 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: 4 Paranoid ActionableScore: 5 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: YES Published priority for this report (same as in Subject): MODERATE 7.0 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).