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  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-74742",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2026-74742"
  ],
  "published": "2026-08-26T14:37:59Z",
  "summary": "veth: fix queue index used to wake the peer txq in veth_poll",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nveth: fix queue index used to wake the peer txq in veth_poll\n\nveth_poll() derives the index of the peer TX queue to wake from\nrq->xdp_rxq.queue_index. That field is only initialized by\nxdp_rxq_info_reg() in veth_enable_xdp_range(), which runs only when an\nXDP program is attached. On the plain GRO/NAPI path\n(veth_napi_enable_range()) xdp_rxq_info_reg() is never called, so\nqueue_index stays 0 for every queue, as priv->rq is zero-allocated.\n\nSo in a multi-queue setup with GRO enabled and no XDP program attached,\nevery NAPI instance looks at the peer's TX queue 0. If veth_xmit() stops\npeer TX queue 1 because the ptr_ring is full (NETDEV_TX_BUSY), nothing\never wakes it again: the poller draining queue 1 wakes queue 0 instead.\nveth implements no ndo_tx_timeout, so the netdev watchdog does not kick\nin either, and the queue stays stopped indefinitely.\n\nDerive the index from the position of the rq within priv->rq instead,\nwhich is correct regardless of whether XDP was ever enabled.\n\nScripts to reproduce the stall are available at\nhttps://github.com/netoptimizer/veth-backpressure-performance-testing",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
    }
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  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-74742"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/b662a1fb4f3a5ea19bac24eea8315b1d05be51e7"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/73f8dd22b1e533a99ecc3f9b5de6c6daccaecace"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/90bb11fb29d3c55a2c46dc7c386d096b286e7fcf"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/60db47f02bfa2aa688938aa199117ec4f8e31d23"
    }
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    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-27T05:18:36Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.5,
      "cvss_v3_severity": "High",
      "scenario": "AV:N - Remote packets routed, NATed, or bridged into a suitably configured container veth reach veth_xmit() and veth_poll() through normal netdev transmit and NAPI softirq paths; no local syscall or physical access is required.\nAC:L - Sustained multi-flow traffic can deterministically fill the ptr_ring on a non-zero RX queue and drive its NAPI poller; waking queue 0 instead of the stopped queue is a logic bug, not a race or layout-dependent condition the attacker cannot control.\nPR:N - Multi-queue veth, GRO, and a non-noqueue qdisc are infrastructure prerequisites, not attacker privileges; forwarded packets traverse veth_xmit/veth_poll with no capability or authentication check, as with CVE-2025-68232 in the same backpressure code.\nUI:N - Exploitation requires only attacker-generated network traffic to drive backpressure on the veth pair; no victim action such as mounting filesystems or opening files is necessary.\nS:U - The defect leaves transmit queues in DRV_XOFF within the host kernel veth driver and does not cross VM, IOMMU, or sandbox security boundaries.\nC:N - The bug only mis-associates NAPI poll instances with peer TX queue indices during wakeup; there is no out-of-bounds access, use-after-free, or other memory read primitive.\nI:N - No memory corruption, arbitrary write, packet tampering, or control-flow influence occurs; the failure is limited to incorrect queue state management on the transmit path.\nA:H - When a non-zero peer TX queue is stopped for a full ptr_ring, veth_poll() never wakes it again and veth has no ndo_tx_timeout recovery, causing an indefinite transmit stall and persistent loss of connectivity on affected queues."
    }
  }
}