From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74260][MODERATE REGULAR] netfilter: nf_dup_netdev: add nf_dev_xmit_recursion*() helpers and use them [ Upstream Date: Sat, 15 Aug 2026 05:30:03 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74260 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: 4 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: edf234f71fb327792196f813048ab8f5bd3bb712 List-Id: CVE: CVE-2026-74260 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: netfilter: nf_dup_netdev: add nf_dev_xmit_recursion*() helpers and use them [ Upstream Commit: edf234f71fb327792196f813048ab8f5bd3bb712 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=edf234f71fb327792196f813048ab8f5bd3bb712 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74260 Analysis date: Sat, 15 Aug 2026 05:30:03 -0400 ActionableScore: 4 ActionableScore lower bound: 3 Actionable bucket: Borderline, manual review recommended / Actionable Moderate only in exposed nft_dup or nft_fwd deployments Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74260 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74260 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: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-74260 MODERATE CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-362;CWE-667;**CWE-400;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.9';DESCR 'nft_dup and nft_fwd used a per CPU recursion counter around skb transmit, but the increment and decrement could become imbalanced if execution migrated to another CPU during dev_queue_xmit or neigh_xmit. This can corrupt recursion accounting for NF_RECURSION_LIMIT and may cause unexpected packet drops, persistent forwarding degradation, or denial of service in systems that use netdev nft_dup or nft_fwd rules. For the CVSS the PR:N is used for the paranoid score because packet traffic can trigger the data path when vulnerable nft_dup or nft_fwd rules already exist, without an account on the target. The issue is network reachable only in deployments where attacker controlled packets can hit these netfilter netdev rules. Impact is denial of service only. No concrete UAF, OOB write, info leak, or privilege escalation primitive is evident from the code change. For the paranoid score, choose the highest still defensible DoS interpretation supported by the bug class and patch context, with preference for manual review sensitivity over autoclosed false negatives.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended / Actionable Moderate only in exposed nft_dup or nft_fwd deployments (with actual score 4) SKIP CVE-2026-74260 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 1d47b55b36d2ec73fe6901212c8b28a593c3b27c YES NO NO unknown MAYBE REMOTE OOB NETFILTER SKB HARDWARE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=3 1. ActionableScore * Conservative score: 3 * Paranoid score: 4 * Final recommended bucket: **Borderline, manual review recommended / Actionable Moderate only in exposed nft_dup or nft_fwd deployments**:: 2. Signal breakdown * Remote reachable / network-triggerable: +2. Attacker controlled packets can reach the affected data path if vulnerable nft_dup or nft_fwd netdev rules already exist. * Common networking core path or packet-processing path: +1. The bug is in netfilter packet forwarding or duplication paths. * Reliable kernel crash / strong DoS: +1 for paranoid only. The patch context supports packet drops or forwarding degradation from imbalanced recursion accounting, but not memory corruption. * Availability impact realistic: +1 for paranoid only. A stuck or imbalanced recursion counter can plausibly cause persistent packet drops on affected paths. * Hard or unreliable race / special timing required: -1. The problematic condition depends on CPU migration during transmit. * No memory corruption signal. The patch does not show UAF, OOB write, double free, type confusion, stale callback, or attacker controlled overwrite. * No privilege escalation signal. The visible primitive is recursion accounting corruption and DoS only. 3. Reachability analysis The trigger is packet traffic through configured nft_dup or nft_fwd netdev rules. Creating such rules normally requires CAP_NET_ADMIN, but once the rules are installed, packet injection may require no local account on the target. Namespaces can lower setup requirements only if an attacker controls a network namespace with relevant nftables permissions, but host impact then depends on how the rules and devices are exposed. This is not a default universal path because it requires specific netfilter rules, but netfilter is common and the affected path is packet-facing when configured. 4. Severity interpretation This behaves more like a borderline Moderate networking DoS than an Important memory-corruption issue. The theoretical worst case is sustained forwarding degradation or packet drops due to broken recursion accounting. Realistic exploitation evidence does not support LPE, confidentiality impact, integrity impact, or kernel code execution. 5. One-sentence report phrase A CPU migration race in netfilter nft_dup and nft_fwd transmit recursion accounting can imbalance per CPU counters and cause packet drops or denial of service when attacker controlled traffic reaches affected netdev rules. 6. Manual review recommendation MANUAL CHECK RECOMMENDED. This is packet-path netfilter code and may be remotely triggerable in configured deployments, but the patch supports DoS only and does not show a concrete memory corruption or privilege escalation primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: netfilter: nf_dup_netdev: add nf_dev_xmit_recursion*() helpers and use them [ Upstream Commit: edf234f71fb327792196f813048ab8f5bd3bb712 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=edf234f71fb327792196f813048ab8f5bd3bb712 Changed files: include/net/netfilter/nf_dup_netdev.h net/netfilter/nf_dup_netdev.c net/netfilter/nft_fwd_netdev.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=edf234f71fb327792196f813048ab8f5bd3bb712 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74260 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74260 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:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.9 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: 3 Paranoid ActionableScore: 4 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).