{
  "threat_severity" : "Moderate",
  "public_date" : "2026-04-22T00:00:00Z",
  "bugzilla" : {
    "description" : "kernel: net: fix fanout UAF in packet_release() via NETDEV_UP race",
    "id" : "2460643",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2460643"
  },
  "cvss3" : {
    "cvss3_base_score" : "6.3",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H",
    "status" : "draft"
  },
  "cwe" : "CWE-364",
  "details" : [ "In the Linux kernel, the following vulnerability has been resolved:\nnet: fix fanout UAF in packet_release() via NETDEV_UP race\n`packet_release()` has a race window where `NETDEV_UP` can re-register a\nsocket into a fanout group's `arr[]` array. The re-registration is not\ncleaned up by `fanout_release()`, leaving a dangling pointer in the fanout\narray.\n`packet_release()` does NOT zero `po->num` in its `bind_lock` section.\nAfter releasing `bind_lock`, `po->num` is still non-zero and `po->ifindex`\nstill matches the bound device. A concurrent `packet_notifier(NETDEV_UP)`\nthat already found the socket in `sklist` can re-register the hook.\nFor fanout sockets, this re-registration calls `__fanout_link(sk, po)`\nwhich adds the socket back into `f->arr[]` and increments `f->num_members`,\nbut does NOT increment `f->sk_ref`.\nThe fix sets `po->num` to zero in `packet_release` while `bind_lock` is\nheld to prevent NETDEV_UP from linking, preventing the race window.\nThis bug was found following an additional audit with Claude Code based\non CVE-2025-38617.", "A flaw was found in the Linux kernel. A race condition in the `packet_release()` function, specifically during a network device up (NETDEV_UP) event, can lead to a Use-After-Free (UAF) vulnerability. This occurs when a socket is re-registered into a fanout group's array, leaving a dangling pointer. A local attacker could potentially exploit this to cause memory corruption, which may result in a denial of service or privilege escalation." ],
  "statement" : "The fix clears `po->num` under `bind_lock` so `NETDEV_UP` cannot re-link a fanout socket mid-release, closing the dangling `f->arr[]` entry found during audit of related fanout bugs. Red Hat recommends patched kernels for any workload using AF_PACKET fanout. Unloading `af_packet` is a blunt mitigation where policy permits.",
  "package_state" : [ {
    "product_name" : "Red Hat Enterprise Linux 10",
    "fix_state" : "Fix deferred",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:10"
  }, {
    "product_name" : "Red Hat Enterprise Linux 6",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Fix deferred",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Fix deferred",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Fix deferred",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Fix deferred",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Fix deferred",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Fix deferred",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2026-31504\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-31504\nhttps://lore.kernel.org/linux-cve-announce/2026042206-CVE-2026-31504-10f4@gregkh/T" ],
  "name" : "CVE-2026-31504",
  "mitigation" : {
    "value" : "To mitigate this issue, prevent the af_packet module from being loaded. See https://access.redhat.com/solutions/41278 for instructions.",
    "lang" : "en:us"
  },
  "csaw" : false
}