{
  "threat_severity" : "Moderate",
  "public_date" : "2026-05-27T00:00:00Z",
  "bugzilla" : {
    "description" : "kernel: net: bridge: use a stable FDB dst snapshot in RCU readers",
    "id" : "2481989",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2481989"
  },
  "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" : "verified"
  },
  "cwe" : "CWE-367",
  "details" : [ "In the Linux kernel, the following vulnerability has been resolved:\nnet: bridge: use a stable FDB dst snapshot in RCU readers\nLocal FDB entries can be rewritten in place by `fdb_delete_local()`, which\nupdates `f->dst` to another port or to `NULL` while keeping the entry\nalive. Several bridge RCU readers inspect `f->dst`, including\n`br_fdb_fillbuf()` through the `brforward_read()` sysfs path.\nThese readers currently load `f->dst` multiple times and can therefore\nobserve inconsistent values across the check and later dereference.\nIn `br_fdb_fillbuf()`, this means a concurrent local-FDB update can change\n`f->dst` after the NULL check and before the `port_no` dereference,\nleading to a NULL-ptr-deref.\nFix this by taking a single `READ_ONCE()` snapshot of `f->dst` in each\naffected RCU reader and using that snapshot for the rest of the access\nsequence. Also publish the in-place `f->dst` updates in `fdb_delete_local()`\nwith `WRITE_ONCE()` so the readers and writer use matching access patterns.", "A flaw was found in the Linux kernel. Inconsistent handling of local Forwarding Database (FDB) entries in the bridge networking component's RCU (Read-Copy-Update) readers can lead to a null-pointer dereference. A local attacker could exploit this by triggering a concurrent update to an FDB entry, causing the system to crash and resulting in a Denial of Service (DoS)." ],
  "statement" : "Bridge FDB RCU readers could load f dst more than once while a local FDB update rewrites that pointer in place to another port or NULL. A concurrent update can make the reader pass a NULL check and later dereference a different NULL value, causing a kernel crash in paths such as br_fdb_fillbuf. Impact is denial of service only.",
  "affected_release" : [ {
    "product_name" : "Red Hat Enterprise Linux 8",
    "release_date" : "2026-07-14T00:00:00Z",
    "advisory" : "RHSA-2026:39180",
    "cpe" : "cpe:/a:redhat:enterprise_linux:8::nfv",
    "package" : "kernel-rt-0:4.18.0-553.144.1.rt7.485.el8_10"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "release_date" : "2026-07-14T00:00:00Z",
    "advisory" : "RHSA-2026:39179",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8",
    "package" : "kernel-0:4.18.0-553.144.1.el8_10"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "release_date" : "2026-07-13T00:00:00Z",
    "advisory" : "RHSA-2026:38491",
    "cpe" : "cpe:/a:redhat:enterprise_linux:9",
    "package" : "kernel-0:5.14.0-687.25.1.el9_8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "release_date" : "2026-07-13T00:00:00Z",
    "advisory" : "RHSA-2026:38491",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9",
    "package" : "kernel-0:5.14.0-687.25.1.el9_8"
  } ],
  "package_state" : [ {
    "product_name" : "Red Hat Enterprise Linux 10",
    "fix_state" : "Affected",
    "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" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2026-46086\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-46086\nhttps://lore.kernel.org/linux-cve-announce/2026052701-CVE-2026-46086-d3c8@gregkh/T" ],
  "name" : "CVE-2026-46086",
  "csaw" : false
}