{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "9466a1ccebbe54ac57fb8a89c2b4b854826546a8"
            },
            {
              "fixed": "64f2c5dd49b956a542c8c02b8dad5d262a462bba"
            },
            {
              "fixed": "51887ccd88791ddaa8755a7c614fda031ecf7982"
            },
            {
              "fixed": "bf19d166337c6488b39cb03eeeffb30a941d6326"
            },
            {
              "fixed": "b878dfdd12d7a5b8722a78d35e313506140ca3d9"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.9.0"
            },
            {
              "fixed": "6.12.109"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.13.0"
            },
            {
              "fixed": "6.18.50"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "7.2.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89554.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction\n\nmptcp_token_join_cookie_init_state() restores remote_nonce, local_nonce,\nbackup, join_id, token and msk from the saved cookie entry when rebuilding\nthe request socket for a MP_JOIN 4th-ACK handled under SYN cookies, but it\ndoes not restore local_id, even though the SYN path saved it.\nsubflow_ulp_clone() then reads that uninitialized field and stores it as\nthe joined subflow's address-ID. Because the request-sock slab is\nSLAB_TYPESAFE_BY_RCU and not zeroed on allocation, the value is the stale\nbyte of a previously freed request socket, which an off-path peer can\ninfluence by sending concurrent MP_JOIN SYNs. This corrupts the path\nmanager's id-based subflow bookkeeping for the connection.\n\nRestore subflow_req-\u003elocal_id from the cookie entry, as done for the other\nfields.",
  "id": "CVE-2026-89554",
  "modified": "2026-09-13T03:30:21.588739468Z",
  "published": "2026-09-11T19:44:27.586Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/51887ccd88791ddaa8755a7c614fda031ecf7982"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/64f2c5dd49b956a542c8c02b8dad5d262a462bba"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b878dfdd12d7a5b8722a78d35e313506140ca3d9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bf19d166337c6488b39cb03eeeffb30a941d6326"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89554.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89554"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.9.0",
  "summary": "mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction"
}