{
  "threat_severity" : "Moderate",
  "public_date" : "2026-03-25T00:00:00Z",
  "bugzilla" : {
    "description" : "kernel: net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop",
    "id" : "2451250",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2451250"
  },
  "cvss3" : {
    "cvss3_base_score" : "5.5",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
    "status" : "draft"
  },
  "cwe" : "CWE-909",
  "details" : [ "In the Linux kernel, the following vulnerability has been resolved:\nnet: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop\nWhen a standalone IPv6 nexthop object is created with a loopback device\n(e.g., \"ip -6 nexthop add id 100 dev lo\"), fib6_nh_init() misclassifies\nit as a reject route. This is because nexthop objects have no destination\nprefix (fc_dst=::), causing fib6_is_reject() to match any loopback\nnexthop. The reject path skips fib_nh_common_init(), leaving\nnhc_pcpu_rth_output unallocated. If an IPv4 route later references this\nnexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and\npanics.\nSimplify the check in fib6_nh_init() to only match explicit reject\nroutes (RTF_REJECT) instead of using fib6_is_reject(). The loopback\npromotion heuristic in fib6_is_reject() is handled separately by\nip6_route_info_create_nh(). After this change, the three cases behave\nas follows:\n1. Explicit reject route (\"ip -6 route add unreachable 2001:db8::/64\"):\nRTF_REJECT is set, enters reject path, skips fib_nh_common_init().\nNo behavior change.\n2. Implicit loopback reject route (\"ip -6 route add 2001:db8::/32 dev lo\"):\nRTF_REJECT is not set, takes normal path, fib_nh_common_init() is\ncalled. ip6_route_info_create_nh() still promotes it to reject\nafterward. nhc_pcpu_rth_output is allocated but unused, which is\nharmless.\n3. Standalone nexthop object (\"ip -6 nexthop add id 100 dev lo\"):\nRTF_REJECT is not set, takes normal path, fib_nh_common_init() is\ncalled. nhc_pcpu_rth_output is properly allocated, fixing the crash\nwhen IPv4 routes reference this nexthop.", "A flaw was found in the Linux kernel's IPv6 networking stack. When a standalone IPv6 nexthop object is created with a loopback device, it is misclassified as a reject route, leading to an unallocated pointer. If an IPv4 route then attempts to reference this nexthop, it causes a NULL pointer dereference. This can result in a kernel panic, leading to a denial of service (DoS) for the system." ],
  "statement" : "This flaw affects systems using advanced routing features with IPv6 nexthop objects on loopback devices. The misclassification causes nhc_pcpu_rth_output to remain unallocated, leading to a panic when IPv4 routes reference the nexthop. Triggering this requires specific routing configuration with nexthop objects on loopback, which is uncommon in typical deployments.",
  "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" : "Out of support scope",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Not affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Not affected",
    "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-2026-23300\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-23300\nhttps://lore.kernel.org/linux-cve-announce/2026032526-CVE-2026-23300-9bc4@gregkh/T" ],
  "name" : "CVE-2026-23300",
  "csaw" : false
}