mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction

{
  "id": "c4512c9b6baf4731200796249f0336ce28c97a922861b41ca51c721a267706a1",
  "url": "https://osv.dev/vulnerability/CVE-2026-89554",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction mptcp_token_join_cookie_init_state() restores remote_nonce, local_nonce, backup, join_id, token and msk from the saved cookie entry when rebuilding the request socket for a MP_JOIN 4th-ACK handled under SYN cookies, but it does not restore local_id, even though the SYN path saved it. subflow_ulp_clone() then reads that uninitialized field and stores it as the joined subflow's address-ID. Because the request-sock slab is SLAB_TYPESAFE_BY_RCU and not zeroed on allocation, the value is the stale byte of a previously freed request socket, which an off-path peer can influence by sending concurrent MP_JOIN SYNs. This corrupts the path manager's id-based subflow bookkeeping for the connection. Restore subflow_req->local_id from the cookie entry, as done for the other fields.",
    "evidence": "osv:CVE-2026-89554",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.270",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.221",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.188",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.157",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.109",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.50",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-89554",
      "aliases": [
        "CVE-2026-89554"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "9466a1ccebbe54ac57fb8a89c2b4b854826546a8"
                },
                {
                  "fixed": "4534e0eead692bb069ad1e6a5a245fc2e2078300"
                },
                {
                  "fixed": "63cacb05e51a1c6e1349d2e593d00fd6ef43def4"
                },
                {
                  "fixed": "954b5ea836eb118d188975ced803448537ab8479"
                },
                {
                  "fixed": "9df36a4846375a9b75bf42d77bfed216b0f366f9"
                },
                {
                  "fixed": "64f2c5dd49b956a542c8c02b8dad5d262a462bba"
                },
                {
                  "fixed": "51887ccd88791ddaa8755a7c614fda031ecf7982"
                },
                {
                  "fixed": "bf19d166337c6488b39cb03eeeffb30a941d6326"
                },
                {
                  "fixed": "b878dfdd12d7a5b8722a78d35e313506140ca3d9"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89554.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.9.0"
                },
                {
                  "fixed": "5.10.270"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.11.0"
                },
                {
                  "fixed": "5.15.221"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.16.0"
                },
                {
                  "fixed": "6.1.188"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.157"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "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"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89554.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:25.477312519Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/4534e0eead692bb069ad1e6a5a245fc2e2078300",
        "https://git.kernel.org/stable/c/51887ccd88791ddaa8755a7c614fda031ecf7982",
        "https://git.kernel.org/stable/c/63cacb05e51a1c6e1349d2e593d00fd6ef43def4",
        "https://git.kernel.org/stable/c/64f2c5dd49b956a542c8c02b8dad5d262a462bba",
        "https://git.kernel.org/stable/c/954b5ea836eb118d188975ced803448537ab8479",
        "https://git.kernel.org/stable/c/9df36a4846375a9b75bf42d77bfed216b0f366f9",
        "https://git.kernel.org/stable/c/b878dfdd12d7a5b8722a78d35e313506140ca3d9",
        "https://git.kernel.org/stable/c/bf19d166337c6488b39cb03eeeffb30a941d6326",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89554.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-89554",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89554.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-89554",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 492145,
  "published_at": "2026-09-11T19:44:27.586+00:00"
}