From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74742][MODERATE REGULAR] veth: fix queue index used to wake the peer txq in veth_poll [ Upstream Date: Wed, 26 Aug 2026 11:16:19 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74742 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: b662a1fb4f3a5ea19bac24eea8315b1d05be51e7 List-Id: CVE: CVE-2026-74742 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: veth: fix queue index used to wake the peer txq in veth_poll [ Upstream Commit: b662a1fb4f3a5ea19bac24eea8315b1d05be51e7 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b662a1fb4f3a5ea19bac24eea8315b1d05be51e7 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74742 Analysis date: Wed, 26 Aug 2026 11:16:19 -0400 ActionableScore: 4 ActionableScore lower bound: 3 Actionable bucket: Borderline, manual review recommended for multitenant container hosts Manual review required: YES Summary: A veth multiqueue TX queue can remain stopped indefinitely because veth_poll wakes the wrong peer queue when XDP was never enabled, allowing a local or container workload to cause a persistent network DoS under specific GRO and backpressure conditions. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74742 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74742 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-2026-74742 MODERATE CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-682;**CWE-400;CWE-703;Other CVSS 'AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.8';DESCR 'A veth multiqueue transmit queue can remain stopped indefinitely because veth_poll used rq xdp_rxq queue_index to choose which peer TX queue to wake. That queue_index is only initialized when XDP is enabled, so on the plain GRO/NAPI path without XDP all receive queues may report index 0 and wake the wrong peer TX queue. An attacker or tenant able to generate traffic through an affected veth pair can trigger backpressure until a nonzero peer TX queue is stopped and never woken again. For the CVSS the PR:L value is used because reliable triggering requires a local process or container workload with access to the affected veth path, not unauthenticated Internet access. The issue is adjacent or local to the host networking setup and is not directly reachable from the public network unless the attacker already controls traffic inside the container or namespace environment. Impact is denial of service for the affected veth networking path only, with no evidence of confidentiality impact, integrity impact, memory corruption, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended for multitenant container hosts (with actual score 4) SKIP CVE-2026-74742 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE INIT NETWORK LINUS QDISC DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScoreLower=3 ActionableScore=4 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 4 * Final recommended bucket: **Borderline, manual review recommended for multitenant container hosts** ## 2. Signal breakdown * Local unprivileged trigger: +1. A local process or container workload can generate traffic through an already configured affected veth pair. * Reliable strong DoS: +1. A nonzero peer TX queue can remain stopped indefinitely because the wrong queue is woken. * Availability impact realistic: +1. veth has no ndo_tx_timeout fallback here, so the stall can persist until administrative recovery or reconfiguration. * Broad or common subsystem exposure: +1. veth is widely used in container and namespace networking. * Hard or configuration dependent trigger: -1. The issue requires multiqueue veth, GRO/NAPI path, no XDP program attached, and enough backpressure to fill the ptr_ring. * Paranoid additional exposure: +1. In container-heavy environments veth is a common packet-processing path and the impact can affect tenant networking reliability. No memory corruption, UAF, OOB write, privilege escalation, confidentiality impact, or integrity impact is supported by the patch. ## 3. Reachability analysis The bug is triggered by traffic through an affected veth pair, not by unauthenticated Internet packets directly. A tenant or local unprivileged process may trigger it if the veth setup already exists and the workload can generate enough traffic to create backpressure. Creating or configuring the multiqueue veth setup usually requires administrative privileges or orchestration control, but using an existing veth interface from inside a container may not. Namespaces matter because veth is commonly exposed to containers, making PR:L more appropriate than PR:H for practical triage. The path is common in container deployments but the exact vulnerable condition is configuration dependent. ## 4. Severity interpretation This behaves like a DoS-only networking logic bug, not an Important-class memory corruption issue. The realistic impact is loss or degradation of connectivity for the affected veth queue or namespace path. Theoretical kernel compromise is not supported because the patch only fixes queue index selection and does not show stale object reuse, attacker-controlled memory corruption, callback corruption, or writable invalid memory access. It is above ordinary Low only because the stall can be persistent and veth is common in container networking. ## 5. One-sentence report phrase A veth multiqueue TX queue can remain stopped indefinitely because veth_poll wakes the wrong peer queue when XDP was never enabled, allowing a local or container workload to cause a persistent network DoS under specific GRO and backpressure conditions. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED. Reason: this is not an Important candidate and has no memory corruption evidence, but the persistent DoS behavior in widely deployed container networking makes it worth manual review for multitenant or production container hosts. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: veth: fix queue index used to wake the peer txq in veth_poll [ Upstream Commit: b662a1fb4f3a5ea19bac24eea8315b1d05be51e7 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b662a1fb4f3a5ea19bac24eea8315b1d05be51e7 Changed files: drivers/net/veth.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=b662a1fb4f3a5ea19bac24eea8315b1d05be51e7 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74742 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74742 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:A/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H 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).