From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-45844][MODERATE REGULAR] netfilter: arp_tables: fix IEEE1394 ARP payload parsing [ Upstream Date: Wed, 27 May 2026 05:55:22 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-45844 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: 3 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: ad9973df8e0eeb123d9ec4d18828e05b7d44ff4b List-Id: CVE: CVE-2026-45844 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: netfilter: arp_tables: fix IEEE1394 ARP payload parsing [ Upstream Commit: ad9973df8e0eeb123d9ec4d18828e05b7d44ff4b Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ad9973df8e0eeb123d9ec4d18828e05b7d44ff4b Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45844 Analysis date: Wed, 27 May 2026 05:55:22 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline, manual review recommended Manual review required: YES Summary: IPv4-over-IEEE1394 ARP packets omit the target hardware address, but arp_tables parsed and mangled them as standard ARP packets, causing incorrect netfilter policy decisions or packet corruption on affected FireWire network configurations. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45844 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45844 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-2026-45844 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H';*CWE-20;CWE-125;CWE-693;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '5.9';DESCR 'IEEE1394 ARP packets omit the target hardware address, but arp_tables parsed the payload as if that field always existed. This can make arptables compare target address fields against wrong bytes and can lead to incorrect filtering decisions where packets are accepted or dropped contrary to policy. The arpt_mangle path can also compute offsets for a standard ARP layout and corrupt the packet when target hardware or target IP mangling is requested on IEEE1394. For the CVSS the PR:N is used for the paranoid score because an adjacent peer can trigger the packet parsing behavior without privileges on the victim once the affected rules are configured. The issue is adjacent network reachable rather than Internet remote. Impact is mainly integrity impact through firewall policy mismatch and availability impact through packet drops or corrupted ARP handling, with no supported evidence of kernel memory corruption or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3) YES REMOTE OOB DANGER NETFILTER NETWORK SKB HARDWARE PACKET DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Borderline, manual review recommended**:: ## 2. Signal breakdown Conservative signals: * Remote or network-triggerable adjacent path: +2. An adjacent IEEE1394 peer can supply ARP traffic that reaches `arp_tables` matching once the affected rules exist. * Integrity impact plausible: +1. Wrong parsing can make arptables compare against incorrect bytes, causing accept or drop decisions contrary to policy. * Physical-only or rare hardware condition: -2. The affected format is IPv4-over-IEEE1394 / FireWire ARP, which is uncommon and requires a specific device type. * Availability impact limited: +1. Incorrect filtering or mangling can drop or corrupt packets, but the patch does not show a kernel crash or system-wide DoS. Conservative total: 2. Paranoid additional signal: * Common packet-processing path: +1. Although IEEE1394 is rare, the bug is in netfilter packet filtering and ARP rule evaluation, so misclassification can affect live packet policy decisions. Paranoid total: 3. No memory corruption signal is counted. The `arpt_mangle` issue corrupts the packet payload due to wrong offset assumptions, not arbitrary kernel memory. No UAF, OOB write into kernel objects, refcount issue, or privilege escalation primitive is supported by the patch. ## 3. Reachability analysis The trigger is adjacent-network traffic on an IEEE1394 interface with relevant arptables rules configured. A remote Internet attacker cannot normally reach this path because ARP over IEEE1394 is local-link only. The attacker does not need privileges on the victim if the vulnerable rules are already installed, but creating or changing arptables rules would normally require administrative privileges. Namespaces and containers do not materially lower the trigger requirement for the packet sender. They may matter only for whoever controls arptables configuration. The affected configuration is not common by default because it depends on FireWire networking and arptables rules that inspect or mangle target fields. ## 4. Severity interpretation This behaves like a specialized netfilter policy-bypass and packet-corruption issue, not an Important-class memory corruption vulnerability. The realistic impact is incorrect filtering or packet drops on a rare adjacent-link configuration. Theoretical kernel exploitation is not supported by the diff because the writes remain within packet data handling and there is no demonstrated overwrite of kernel control data. Overall this is borderline and worth manual review mainly because it affects packet-filtering semantics, but it is not an Actionable Moderate or Important candidate based on the provided evidence. ## 5. One-sentence report phrase IPv4-over-IEEE1394 ARP packets omit the target hardware address, but arp_tables parsed and mangled them as standard ARP packets, causing incorrect netfilter policy decisions or packet corruption on affected FireWire network configurations. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED. Reason: the issue is not memory corruption and exposure is rare, but it affects netfilter packet policy decisions and has adjacent-network triggerability when IEEE1394 ARP filtering or mangling rules are present. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: netfilter: arp_tables: fix IEEE1394 ARP payload parsing [ Upstream Commit: ad9973df8e0eeb123d9ec4d18828e05b7d44ff4b Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ad9973df8e0eeb123d9ec4d18828e05b7d44ff4b Changed files: net/ipv4/arp.c net/ipv4/netfilter/arp_tables.c net/ipv4/netfilter/arpt_mangle.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=ad9973df8e0eeb123d9ec4d18828e05b7d44ff4b ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45844 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45844 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:L/A:L The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:L/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: 2 Paranoid ActionableScore: 3 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).