{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "b19bc2945b40b9fd38e835700907ffe8534ef0de"
            },
            {
              "fixed": "f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47"
            },
            {
              "fixed": "fb1f54b7d16f393b8b65d328410f78b4beea8fcc"
            },
            {
              "fixed": "3fd6547f5b8ac99687be6d937a0321efda760597"
            },
            {
              "fixed": "eb9c6aeb512f877cf397deb1e4526f646c70e4a7"
            },
            {
              "fixed": "15fa9ead4d5e6b6b9c794e84144146c917f2cb62"
            },
            {
              "fixed": "b313e9037d98c13938740e5ebda7852929366dff"
            },
            {
              "fixed": "9b55b253907e7431210483519c5ad711a37dafa1"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.12.0"
            },
            {
              "fixed": "5.15.203"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "5.16.0"
            },
            {
              "fixed": "6.1.169"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.2.0"
            },
            {
              "fixed": "6.6.135"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.7.0"
            },
            {
              "fixed": "6.12.82"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.13.0"
            },
            {
              "fixed": "6.18.23"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "6.19.13"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31669.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: fix slab-use-after-free in __inet_lookup_established\n\nThe ehash table lookups are lockless and rely on\nSLAB_TYPESAFE_BY_RCU to guarantee socket memory stability\nduring RCU read-side critical sections. Both tcp_prot and\ntcpv6_prot have their slab caches created with this flag\nvia proto_register().\n\nHowever, MPTCP's mptcp_subflow_init() copies tcpv6_prot into\ntcpv6_prot_override during inet_init() (fs_initcall, level 5),\nbefore inet6_init() (module_init/device_initcall, level 6) has\ncalled proto_register(\u0026tcpv6_prot). At that point,\ntcpv6_prot.slab is still NULL, so tcpv6_prot_override.slab\nremains NULL permanently.\n\nThis causes MPTCP v6 subflow child sockets to be allocated via\nkmalloc (falling into kmalloc-4k) instead of the TCPv6 slab\ncache. The kmalloc-4k cache lacks SLAB_TYPESAFE_BY_RCU, so\nwhen these sockets are freed without SOCK_RCU_FREE (which is\ncleared for child sockets by design), the memory can be\nimmediately reused. Concurrent ehash lookups under\nrcu_read_lock can then access freed memory, triggering a\nslab-use-after-free in __inet_lookup_established.\n\nFix this by splitting the IPv6-specific initialization out of\nmptcp_subflow_init() into a new mptcp_subflow_v6_init(), called\nfrom mptcp_proto_v6_init() before protocol registration. This\nensures tcpv6_prot_override.slab correctly inherits the\nSLAB_TYPESAFE_BY_RCU slab cache.",
  "id": "CVE-2026-31669",
  "modified": "2026-07-08T05:38:37.869484878Z",
  "published": "2026-04-24T14:45:17.295Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/15fa9ead4d5e6b6b9c794e84144146c917f2cb62"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3fd6547f5b8ac99687be6d937a0321efda760597"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9b55b253907e7431210483519c5ad711a37dafa1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b313e9037d98c13938740e5ebda7852929366dff"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/eb9c6aeb512f877cf397deb1e4526f646c70e4a7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/fb1f54b7d16f393b8b65d328410f78b4beea8fcc"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31669.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31669"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.7.5",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "mptcp: fix slab-use-after-free in __inet_lookup_established"
}