From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74709][LOW] xsk: clear metadata pointer when no timestamp is requested [ Upstream Date: Sat, 22 Aug 2026 13:30:02 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74709 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: 1 X-AL-KERNEL-Commit: 0ba2e1eb07a826d021344e2f146b6716c58139eb List-Id: CVE: CVE-2026-74709 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: xsk: clear metadata pointer when no timestamp is requested [ Upstream Commit: 0ba2e1eb07a826d021344e2f146b6716c58139eb Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0ba2e1eb07a826d021344e2f146b6716c58139eb Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74709 Analysis date: Sat, 22 Aug 2026 13:30:02 -0400 ActionableScore: 2 ActionableScore lower bound: 1 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: AF_XDP Tx metadata completion can write an unexpected hardware timestamp into the metadata area when mutable flags are reread after request processing, but the write remains bounded and does not demonstrate kernel memory corruption, privilege escalation, or remote reachability. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74709 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74709 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-2026-74709 LOW CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N';CWE-367;CWE-362;*CWE-20;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N';BEST CVSS score: '3.6';DESCR 'AF_XDP Tx metadata handling can use mutable user supplied flags inconsistently between request processing and completion. A local process can change metadata flags after the transmit request is processed, causing completion code to write a timestamp even though timestamp completion was not requested when the packet was submitted. The affected mlx5 multi packet WQE path evaluates metadata per batch, so descriptors after the first one in a session may still receive a timestamp completion based on stale pointer state. For the CVSS the PR:L is used because exploitation requires local ability to create or use an AF_XDP Tx path with metadata support, which may be available to a service account or a container with delegated network capability rather than full host root. The issue is not directly network reachable and the documented write stays inside the metadata area. Impact is limited to unintended metadata modification and possible low information exposure of timing data, with no evidence of kernel memory corruption, privilege escalation, or system wide DoS.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2) YES REMOTE SIMPLEFIX HARDWARE PACKET DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=1 ## 1. ActionableScore * Conservative score: 1 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown * +1 Integrity impact plausible: completion may write a timestamp that was not requested at submission time, modifying user-visible Tx metadata unexpectedly. * +1 Local trigger in paranoid interpretation: a local process with access to the affected AF_XDP Tx metadata path may influence metadata flags between request processing and completion. * +0 Generic memory corruption: not awarded. The commit explicitly says the write stays inside the metadata area. * +0 Strong DoS: not awarded. No crash, panic, UAF, OOB write, or persistent device failure is described. * +0 High-control API bonus: not awarded. AF_XDP is a rich data-plane API, but this specific bug does not show attacker control over kernel object lifetime, reclaim, callback targets, or memory layout. * +0 Remote reachable: not awarded. This is not packet-triggered by a remote host. * +0 LPE plausible: not awarded. There is no demonstrated privilege boundary bypass or kernel memory corruption primitive. ## 3. Reachability analysis The bug requires a local actor able to use an AF_XDP Tx metadata path. In typical deployments, setting up AF_XDP with XDP and hardware offloads may require privileged network configuration such as CAP_NET_ADMIN, CAP_BPF, or a preconfigured service. Namespace or container delegation could make the path reachable to a reduced-privilege service account, but this is still not a remote network trigger. The most specific affected case is the mlx5 multi-packet WQE path, while single-WQE, other zero-copy, and generic paths are described as unaffected. ## 4. Severity interpretation This behaves more like an ordinary Moderate or Low-like correctness/security issue than an Important-class kernel vulnerability. The theoretical concern is inconsistent use of mutable metadata flags, but the realistic demonstrated effect is a bounded timestamp write inside the intended metadata area. There is no evidence of UAF, OOB access, arbitrary write, type confusion, privilege escalation, or reliable kernel crash. ## 5. One-sentence report phrase AF_XDP Tx metadata completion can write an unexpected hardware timestamp into the metadata area when mutable flags are reread after request processing, but the write remains bounded and does not demonstrate kernel memory corruption, privilege escalation, or remote reachability. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED The issue can be auto-closed for urgent triage purposes because the patch and commit constrain the impact to metadata-area modification, with no demonstrated kernel memory corruption, LPE path, remote trigger, or strong DoS. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: xsk: clear metadata pointer when no timestamp is requested [ Upstream Commit: 0ba2e1eb07a826d021344e2f146b6716c58139eb Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0ba2e1eb07a826d021344e2f146b6716c58139eb Changed files: include/net/xdp_sock.h net/xdp/xsk.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=0ba2e1eb07a826d021344e2f146b6716c58139eb ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74709 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74709 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:N/I:L/A:N The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N The Best / paranoid CVSS score: 3.6 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: 1 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).