{
  "cveId": "CVE-2026-52940",
  "url": "https://patchblox.com/security/cve/CVE-2026-52940",
  "summary": "CVE-2026-52940 is fixed in 20 products on 1 platform, first by DEBIAN-CVE-2026-52940, released June 28, 2026. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "linux: In the Linux kernel, the following vulnerability has been resolved:  tun: zero the whole vnet header in tun_put_user(...",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  tun: zero the whole vnet header in tun_put_user()  tun_put_user() declares an on-stack struct virtio_net_hdr_v1_hash_tunnel without zeroing it. For a non-tunnel skb, virtio_net_hdr_tnl_from_skb() only initializes the first 10 bytes (sizeof(struct virtio_net_hdr)), leaving bytes 10..23 (num_buffers and the hash/tunnel fields) as stack garbage.  An unprivileged user can set the vnet header size to 24 with TUNSETVNETHDRSZ, so __tun_vnet_hdr_put() copies all 24 bytes of the partially-initialized struct to userspace, leaking 14 bytes of kernel stack on every read of a non-tunnel packet.  Fix it the same way tun_get_user() already does by zeroing the whole header right after declaration.",
  "published": "2026-06-24T08:16:24Z",
  "severity": "medium",
  "cvss": 5.5,
  "cvssVector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
  "epss": 0.0016,
  "epssPercentile": 0.05211,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "fixes": [
    {
      "platform": "linux",
      "product": "bpftool6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "bpftool6.18-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel-livepatch-6.18.36-69.134",
      "release": "amzn 2023",
      "fixedVersion": "1:1.0-0.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-debuginfo-common-aarch64",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-debuginfo-common-x86_64",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-devel",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-headers",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-modules-extra",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-modules-extra-common",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-tools",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-tools-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-tools-devel",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.0.13-1",
      "fix": "DEBIAN-CVE-2026-52940",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-52940",
      "released": "2026-06-28T17:47:07Z"
    },
    {
      "platform": "linux",
      "product": "microvm-kernel6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "perf6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "perf6.18-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "python3-perf6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "python3-perf6.18-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.36-69.134.amzn2023",
      "fix": "ALAS2023-2026-1925",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1925",
      "released": "2026-07-06T09:00:00Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T19:12:23Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}