From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-72349][MODERATE REGULAR] netfilter: xt_rateest: fix u64 truncation in xt_rateest_mt() [ Upstream Date: Sat, 15 Aug 2026 06:49:57 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-72349 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: 77e9ba358d63fe2eb03c90d29ea85651d95cf2e6 List-Id: CVE: CVE-2026-72349 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: netfilter: xt_rateest: fix u64 truncation in xt_rateest_mt() [ Upstream Commit: 77e9ba358d63fe2eb03c90d29ea85651d95cf2e6 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=77e9ba358d63fe2eb03c90d29ea85651d95cf2e6 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72349 Analysis date: Sat, 15 Aug 2026 06:49:57 -0400 ActionableScore: 4 ActionableScore lower bound: 3 Actionable bucket: Borderline Moderate / manual review recommended Manual review required: YES Summary: A u32 truncation bug in xt_rateest_mt() can cause incorrect RATEEST match results on high-speed links, potentially leading to wrong netfilter policy decisions when xt_rateest rules are deployed. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72349 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72349 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-2026-72349 MODERATE CHECK WITH IMPACT FROM ORIG NN IMPORTANT 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:L/A:L';CWE-190;CWE-681;CWE-682;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N';BEST CVSS score: '4.8';DESCR 'xt_rateest uses u32 local variables for byte and packet rate comparisons even though gen_estimator_read can provide u64 rate values. On links faster than about 34 Gbps, the byte rate can exceed the u32 range and the truncated value can make a netfilter RATEEST match return the wrong result. A remote traffic source may influence the measured rate if the host uses xt_rateest rules on a high speed interface, but reliable impact depends on a specific firewall or routing policy that trusts this match. For the CVSS the PR:N is used because no account on the target is needed when an already configured rule processes attacker controlled traffic. The issue is network reachable through packet processing, but the attack complexity is high due to the required link speed and configuration. Impact is a possible integrity policy bypass and in some deployments limited availability impact from wrong accept drop or path selection decisions. There is no evidence of memory corruption, information leak, or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline Moderate / manual review recommended (with actual score 4) YES REMOTE SIMPLEFIX NETFILTER LINUS LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 4 * Final recommended bucket: **Borderline Moderate / manual review recommended**:: ## 2. Signal breakdown Conservative signals: * Remote reachable / network-triggerable: +2 * Packets can influence the rate estimator when an existing xt_rateest rule processes attacker-controlled traffic. * Integrity impact plausible: +1 * Incorrect truncation can make RATEEST matching return the wrong result, potentially causing wrong accept/drop/mark/routing policy decisions. * Common networking / packet-processing path: +1 * The affected code is in netfilter packet matching. * Rare AND difficult-to-reach configuration: -1 * Practical impact requires xt_rateest rules and traffic rates above about 34 Gbps, which is not a default or common deployment condition. Paranoid additional signal: * Availability impact realistic: +1 * In some configurations, wrong match results could degrade service availability through incorrect traffic handling, but there is no kernel crash or memory corruption. No memory corruption, UAF, OOB access, arbitrary write, LPE primitive, or information leak is supported by the patch. ## 3. Reachability analysis The bug can be influenced by a remote traffic source only if the target already has xt_rateest-based netfilter rules configured and processes sufficiently high traffic rates. The attacker does not need a local account in that scenario, but the vulnerable policy must already be installed by an administrator. Namespaces do not significantly improve attacker reachability unless an untrusted tenant can control or trigger relevant netfilter rules and high-rate traffic paths. This is not a default-exposed bug in generic packet handling. Call-site confidence: high, because the patch directly changes the match function used in the packet-processing path. ## 4. Severity interpretation This behaves like a correctness and policy-classification bug, not a memory-safety vulnerability. The realistic impact is wrong firewall or traffic-control decisions on high-speed links using xt_rateest. Theoretical consequences can include limited integrity impact and possibly limited availability impact, but there is no evidence of privilege escalation, kernel crash, or confidentiality exposure. ## 5. One-sentence report phrase A u32 truncation bug in xt_rateest_mt() can cause incorrect RATEEST match results on high-speed links, potentially leading to wrong netfilter policy decisions when xt_rateest rules are deployed. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: the issue is network-influenced in configured high-speed netfilter deployments, but the impact is policy misclassification rather than memory corruption or a demonstrated privilege-escalation path. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: netfilter: xt_rateest: fix u64 truncation in xt_rateest_mt() [ Upstream Commit: 77e9ba358d63fe2eb03c90d29ea85651d95cf2e6 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=77e9ba358d63fe2eb03c90d29ea85651d95cf2e6 Changed files: net/netfilter/xt_rateest.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=77e9ba358d63fe2eb03c90d29ea85651d95cf2e6 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72349 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72349 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:L/A:N The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L The Best / paranoid CVSS score: 4.8 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).