From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74710][MODERATE REGULAR] xsk: require at least 16 bytes of TX metadata [ Upstream Date: Sat, 22 Aug 2026 14:35:38 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74710 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: 21b8536aee819792f1b4b38b9aacf2a073025d49 List-Id: CVE: CVE-2026-74710 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: xsk: require at least 16 bytes of TX metadata [ Upstream Commit: 21b8536aee819792f1b4b38b9aacf2a073025d49 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=21b8536aee819792f1b4b38b9aacf2a073025d49 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74710 Analysis date: Sat, 22 Aug 2026 14:35:38 -0400 ActionableScore: 4 ActionableScore lower bound: 3 Actionable bucket: Borderline manual review recommended / ordinary Moderate if no disclosure path is found Manual review required: YES Summary: AF_XDP allowed an invalid 8 byte TX metadata length, letting the kernel read beyond the registered TX metadata area during transmit metadata processing, with local PR:L reachability and limited integrity or disclosure concern but no demonstrated privilege escalation primitive. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74710 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74710 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-2026-74710 MODERATE 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:L/I:L/A:L';CWE-125;*CWE-20;CWE-119;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N';BEST CVSS score: '5.3';DESCR 'AF_XDP accepted a TX metadata length of 8 bytes even though supported TX metadata requests need the flags field plus at least one 8 byte request field. This can make the kernel read past the registered TX metadata area when processing transmit metadata for an XSK UMEM. For the CVSS the PR:L is used because triggering requires a local process that can create and configure AF_XDP UMEM state, but it does not require network reachability to the host. The issue is not directly network reachable and is triggered through a local socket and UMEM registration path. Impact is expected to be limited, but the concrete out-of-bounds read makes limited confidentiality or integrity impact plausible enough for manual review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / ordinary Moderate if no disclosure path is found (with actual score 4) YES SIMPLEFIX YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 4 * Final recommended bucket: **Borderline manual review recommended / ordinary Moderate if no disclosure path is found**:: ## 2. Signal breakdown Conservative signals: * Local unprivileged or low-privilege trigger: +1 Triggering requires a local process able to create and configure AF_XDP UMEM state. This is local PR:L rather than remote. * Memory layout invariant restoration: +1 The patch restores a minimum TX metadata layout invariant. Supported requests require flags plus at least one 8 byte request field, so 8 bytes is structurally invalid. * Integrity impact plausible: +1 The kernel may interpret bytes beyond the registered metadata area as TX metadata fields, which can cause unintended TX metadata behavior. Paranoid additional signal: * Limited confidentiality or availability concern: +1 The issue is a concrete out-of-bounds read beyond the registered metadata area, but no kernel memory disclosure, write primitive, UAF, type confusion, or controlled corruption primitive is shown. Not awarded: * Remote reachable: +0 This is not network-triggerable by packet input. * Strong memory corruption: +0 The patch shows read beyond registered metadata, not OOB write, UAF, double free, or arbitrary write. * Strong LPE plausibility: +0 No reclaim, overwrite, callback control, object confusion, or privilege escalation primitive is demonstrated. * Reliable kernel crash: +0 The commit does not show a reliable panic or system-wide crash path. ## 3. Reachability analysis The bug is reachable through local AF_XDP UMEM registration and later TX metadata processing. A local process needs permission to use the relevant AF_XDP path and network device setup. In many deployments, practical AF_XDP use may depend on CAP_NET_RAW, CAP_NET_ADMIN, an already attached XDP program, or administrator-provided networking setup, so the trigger is not purely remote and not always available to arbitrary users. Namespaces or delegated network capabilities can lower the practical privilege requirement, so PR:L is the safer triage assumption. The path is not default Internet-exposed. Call-site confidence: medium. The patch identifies the validation point and the downstream effect, but the exact later read sites and read-back behavior are not included in the supplied diff. ## 4. Severity interpretation This behaves more like a borderline Moderate than an Important issue. The concrete primitive is a local bounds validation bug causing a read beyond the registered TX metadata area. Realistic exploitation evidence supports limited integrity concern and possibly limited disclosure or availability concern, but not privilege escalation or strong memory corruption. The paranoid score remains manual-review worthy because AF_XDP is a high-performance networking data path and the bug is a real OOB read condition. ## 5. One-sentence report phrase AF_XDP allowed an invalid 8 byte TX metadata length, letting the kernel read beyond the registered TX metadata area during transmit metadata processing, with local PR:L reachability and limited integrity or disclosure concern but no demonstrated privilege escalation primitive. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Manual review is recommended because this is a concrete OOB read in a kernel networking data path, but it should not be treated as Important without evidence of kernel memory disclosure, write corruption, reliable crash, or LPE. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: xsk: require at least 16 bytes of TX metadata [ Upstream Commit: 21b8536aee819792f1b4b38b9aacf2a073025d49 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=21b8536aee819792f1b4b38b9aacf2a073025d49 Changed files: net/xdp/xdp_umem.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=21b8536aee819792f1b4b38b9aacf2a073025d49 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74710 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74710 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:L/A:N The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L The Best / paranoid CVSS score: 5.3 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).