From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74558][LOW] xsk: reclaim invalid Tx descriptors in ZC batch path [ Upstream Date: Sat, 15 Aug 2026 09:14:32 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74558 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 2 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: e7ce2bad0c33471c8da4dd73dff2119a68f96f3a List-Id: CVE: CVE-2026-74558 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: xsk: reclaim invalid Tx descriptors in ZC batch path [ Upstream Commit: e7ce2bad0c33471c8da4dd73dff2119a68f96f3a Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e7ce2bad0c33471c8da4dd73dff2119a68f96f3a Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74558 Analysis date: Sat, 15 Aug 2026 09:14:32 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: AF_XDP zero-copy multi-buffer Tx can consume invalid or oversized descriptors without returning the referenced UMEM frames through the completion ring, allowing a local AF_XDP-capable process to stall the affected Tx path or shared UMEM pool. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74558 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74558 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: LOW Manual review required: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-74558 LOW CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-664;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'AF_XDP zero-copy multi-buffer Tx can consume invalid or oversized Tx descriptors without returning the referenced UMEM frames through the completion ring. This breaks UMEM ownership accounting and can leave frames unreclaimed by userspace, which may stall the affected Tx path or a shared UMEM pool. For the CVSS the PR:L is used because a local process must be able to create and drive an AF_XDP socket and provide crafted Tx descriptors. The issue is not directly network reachable because it is triggered by local AF_XDP control of the Tx ring rather than by received packets. Impact is primarily denial of service for the affected socket, queue, or datapath. No clear UAF, OOB access, arbitrary write, information leak, or privilege escalation primitive is visible from the patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2) YES REMOTE OOB LOCK DANGER SKB HARDWARE PACKET DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / Low-like** ## 2. Signal breakdown Triggered signals: * Local low-privileged or delegated AF_XDP trigger: +1 A local process that can create and drive an AF_XDP zero-copy multi-buffer Tx socket can craft invalid or oversized Tx descriptors. * Availability impact realistic: +1 Lost UMEM frame completions can stall the affected Tx path, socket, queue, or shared UMEM pool. Not triggered: * Remote reachable: +0 This is not triggered by incoming network packets alone. * Generic memory corruption: +0 The patch shows descriptor ownership and completion accounting issues, not UAF, OOB write, double free, type confusion, or arbitrary write. * Privilege escalation plausible: +0 No supported LPE primitive is visible. * Reliable kernel crash / strong DoS: +0 The impact is mainly datapath stall or resource ownership loss, not a demonstrated kernel panic. * Rare / special configuration: not subtracted in the main score AF_XDP zero-copy multi-buffer Tx is configuration-dependent, but AF_XDP is still an ordinary local kernel networking interface in relevant deployments. ## 3. Reachability analysis The bug is reachable by a local process that can use AF_XDP zero-copy Tx with multi-buffer descriptors and can submit malformed or oversized Tx packets. In many production deployments this is limited to privileged packet-processing services or processes with delegated networking capabilities, not arbitrary remote attackers. Namespaces or containers may matter if AF_XDP access and device queue ownership are delegated into the container, but the issue still requires local control of the Tx ring. The path is not broadly default-exposed and depends on AF_XDP, zero-copy support, suitable NIC or driver support, and multi-buffer Tx use. ## 4. Severity interpretation This behaves like an ordinary Moderate or Low-like resource ownership bug, not an Important-class memory corruption issue. The realistic effect is denial of service or Tx datapath stall due to UMEM frames not being returned through the completion ring. Theoretical concern is limited because the patch does not show kernel object lifetime corruption, attacker-controlled overwrite, stale callback, UAF reclaim, info leak, or privilege escalation. ## 5. One-sentence report phrase AF_XDP zero-copy multi-buffer Tx can consume invalid or oversized descriptors without returning the referenced UMEM frames through the completion ring, allowing a local AF_XDP-capable process to stall the affected Tx path or shared UMEM pool. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can be handled as an ordinary Moderate / Low-like issue because the patch supports a local resource ownership and availability impact only, with no concrete memory corruption or privilege escalation primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: xsk: reclaim invalid Tx descriptors in ZC batch path [ Upstream Commit: e7ce2bad0c33471c8da4dd73dff2119a68f96f3a Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e7ce2bad0c33471c8da4dd73dff2119a68f96f3a Changed files: include/net/xsk_buff_pool.h net/xdp/xsk.c net/xdp/xsk_buff_pool.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=e7ce2bad0c33471c8da4dd73dff2119a68f96f3a ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74558 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74558 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:L/PR:L/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.5 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: unknown Paranoid ActionableScore: 2 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: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW 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).