From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64037][IMPORTANT] wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled [ Upstream Date: Sun, 19 Jul 2026 17:52:16 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64037 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 8 X-AL-KERNEL-ActionableScore-Lower: 5 X-AL-KERNEL-Commit: 9e360e610a73f62432e986775023d5382773f045 List-Id: CVE: CVE-2026-64037 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: YES Patch: wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled [ Upstream Commit: 9e360e610a73f62432e986775023d5382773f045 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9e360e610a73f62432e986775023d5382773f045 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64037 Analysis date: Sun, 19 Jul 2026 17:52:16 -0400 ActionableScore: 8 ActionableScore lower bound: 5 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: An iwlwifi MLD TSO arithmetic bug can turn an AMSDU-disabled sentinel value into gso_size 0, causing a massive segmentation burst and TX completion storm that may lead to TCP skb lifetime corruption, UAF, refcount underflow, and kernel crash. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64037 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64037 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: IMPORTANT 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-2026-64037 IMPORTANT CHECK WITH IMPACT FROM ORIG NN IMPORTANT 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-682;**CWE-400;*CWE-416;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.5';DESCR 'An integer corner case in the iwlwifi MLD TSO path can make num_subframes become zero when AMSDU is disabled for a TID and max_tid_amsdu_len is set to the sentinel value 1. The zero value can propagate into the TSO segmentation helper as gso_size 0, causing skb_gso_segment to create a very large number of tiny segments from one GSO skb and flooding the TX path. The described failure mode includes memory corruption and a subsequent use after free in the TCP retransmit queue, with refcount underflow in tcp_shifted_skb and possible NULL dereference in tcp_rack_detect_loss. For the CVSS the PR:N is used in the paranoid score because an adjacent wireless attacker or malicious AP may be able to influence the wireless link state that disables AMSDU, while normal traffic from the victim can exercise the transmit path. The issue is not Internet routable and is best treated as adjacent or local depending on the deployment. Impact is at least denial of service via kernel crash and may include confidentiality or integrity impact if the UAF is controllable.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7) YES REMOTE OOB DANGER UAF NETWORK SKB KPANIC YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=8 ActionableScoreLower=5 ## 1. ActionableScore * Conservative score: 5 * Paranoid score: 8 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Firmware-mediated external influence: +1. AMSDU disablement comes from TLC or firmware driven station state rather than a direct userspace value. * Local unprivileged trigger: +1. A local user may be able to generate TCP GSO traffic over the affected Wi-Fi device once the bad AMSDU state exists. * Weak LPE concern: +1. The commit describes memory corruption and UAF symptoms, but does not demonstrate attacker-controlled reclaim, replacement, or write control. * Memory corruption, strong primitive: +2. The described downstream failure includes memory corruption and a use-after-free in TCP retransmit handling. * Real lifetime corruption: +1. The failure mode includes UAF and refcount underflow in TCP skb handling. * Reliable kernel crash / strong DoS: +1. NULL dereference and TX completion storm make kernel crash realistic. * Hard or condition-dependent trigger: -1. Requires iwlwifi MLD, AMSDU disabled sentinel state, GSO/TSO traffic, and the specific segmentation path. * Corruption primitive constrained or not yet controlled: -1. The patch does not show an attacker-controlled payload, target selection, or reclaim primitive. Conservative total: 5. Paranoid additions / changes: * Privilege escalation plausible, stronger interpretation: +2 instead of +1. UAF plus refcount underflow in TCP skb lifetime code is a class that deserves manual review even without a published exploit primitive. * Broad deployed exposure: +1. Intel Wi-Fi and TCP/GSO transmit paths are common enough that this should not be treated as an obscure-only issue. Paranoid total: 8. Call-site confidence: medium. The patch shows the immediate arithmetic and fallback site, while the deeper TCP UAF path is described by the commit message rather than fully shown in the diff. ## 3. Reachability analysis The most realistic trigger is local unprivileged traffic generation over an affected Intel iwlwifi MLD device after AMSDU has been disabled for a TID. A malicious or unusual wireless environment may influence the firmware/TLC state that disables AMSDU, but the bug is not Internet-routable and should not be treated as ordinary AV:N remote reachability. Namespaces and containers may matter if a containerized workload can send traffic through the host Wi-Fi device, but the hardware and driver state remain host-controlled. No CAP_SYS_ADMIN or CAP_NET_ADMIN is inherently required just to generate TCP traffic, so PR:L is realistic for the local path. For the paranoid interpretation, PR:N-like adjacent influence is considered only through malicious AP or wireless environment control plus victim traffic, not as direct remote packet parsing. The path is not universally enabled on all systems because it requires the iwlwifi MLD subdriver and affected hardware/firmware behavior. Still, the affected components are common enough that this should not be auto-closed as niche. ## 4. Severity interpretation This behaves above ordinary Moderate because the commit does not merely describe a WARN or resource exhaustion. It explicitly connects the segmentation explosion to memory corruption, TCP retransmit queue UAF, refcount underflow, and NULL dereference. Realistically demonstrated impact is strong DoS and kernel crash under specific Wi-Fi and traffic conditions. Theoretical impact includes possible LPE if the UAF or refcount corruption can be shaped into controlled object reuse, but that is not demonstrated by the patch. Therefore the conservative score is Actionable Moderate, while the paranoid score is a Strong Important candidate for manual review. ## 5. One-sentence report phrase An iwlwifi MLD TSO arithmetic bug can turn an AMSDU-disabled sentinel value into gso_size 0, causing a massive segmentation burst and TX completion storm that may lead to TCP skb lifetime corruption, UAF, refcount underflow, and kernel crash. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the patch context explicitly mentions memory corruption and UAF in TCP retransmit handling, and the affected path is reachable through ordinary traffic once the Wi-Fi driver reaches the AMSDU-disabled state. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled [ Upstream Commit: 9e360e610a73f62432e986775023d5382773f045 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9e360e610a73f62432e986775023d5382773f045 Changed files: drivers/net/wireless/intel/iwlwifi/mld/tx.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=9e360e610a73f62432e986775023d5382773f045 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64037 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64037 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:H/PR:L/UI:N/S:U/C:L/I:L/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: 5 Paranoid ActionableScore: 8 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: IMPORTANT KPANIC detected for this report: YES Published priority for this report (same as in Subject): IMPORTANT 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).