{
  "threat_severity" : "Moderate",
  "public_date" : "2025-04-01T00:00:00Z",
  "bugzilla" : {
    "description" : "kernel: vlan: enforce underlying device type",
    "id" : "2356639",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2356639"
  },
  "cvss3" : {
    "cvss3_base_score" : "7.1",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
    "status" : "verified"
  },
  "cwe" : "CWE-125",
  "details" : [ "In the Linux kernel, the following vulnerability has been resolved:\nvlan: enforce underlying device type\nCurrently, VLAN devices can be created on top of non-ethernet devices.\nBesides the fact that it doesn't make much sense, this also causes a\nbug which leaks the address of a kernel function to usermode.\nWhen creating a VLAN device, we initialize GARP (garp_init_applicant)\nand MRP (mrp_init_applicant) for the underlying device.\nAs part of the initialization process, we add the multicast address of\neach applicant to the underlying device, by calling dev_mc_add.\n__dev_mc_add uses dev->addr_len to determine the length of the new\nmulticast address.\nThis causes an out-of-bounds read if dev->addr_len is greater than 6,\nsince the multicast addresses provided by GARP and MRP are only 6\nbytes long.\nThis behaviour can be reproduced using the following commands:\nip tunnel add gretest mode ip6gre local ::1 remote ::2 dev lo\nip l set up dev gretest\nip link add link gretest name vlantest type vlan id 100\nThen, the following command will display the address of garp_pdu_rcv:\nip maddr show | grep 01:80:c2:00:00:21\nFix the bug by enforcing the type of the underlying device during VLAN\ndevice initialization." ],
  "affected_release" : [ {
    "product_name" : "Red Hat Enterprise Linux 9",
    "release_date" : "2025-06-09T00:00:00Z",
    "advisory" : "RHSA-2025:8643",
    "cpe" : "cpe:/a:redhat:enterprise_linux:9",
    "package" : "kernel-0:5.14.0-570.21.1.el9_6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "release_date" : "2025-06-09T00:00:00Z",
    "advisory" : "RHSA-2025:8643",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9",
    "package" : "kernel-0:5.14.0-570.21.1.el9_6"
  } ],
  "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" : "Out of support scope",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Out of support scope",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Out of support scope",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Out of support scope",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "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-2025-21920\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-21920\nhttps://lore.kernel.org/linux-cve-announce/2025040131-CVE-2025-21920-08ff@gregkh/T" ],
  "name" : "CVE-2025-21920",
  "csaw" : false
}